Yoshinori Sasaki was born on July 23, 1974 in Osaka-shi, Osaka, Japan.

Yoshinori's first athletic competition took place in high school as he got into sumo wrestling. He became a third-rank junior champion while participating against kids his own age, and at the age of 16 in 1990 would begin training to become a professional sumo wrestler.

In January 1993, Sasaki made his official debut wrestling as a sumo wrestler but did not gather much success right away as he would be ranked the second lowest in the sport at one time. While in sumo, his love pro wrestling never stopped as he would wear a t-shirt of his favorite promotion FMW to the ring for one of his sumo matches. Sasaki would end up improving greatly by 1995 and make it to the the fourth highest division in Sumo the Sandanme division. He would also become Akebono's assistant during his time in Sumo. 

In September 1995, while training for a match, Sasaki would end up injuring his right ligament which doctors would say would put him out of any kind of action for 9 months. Sasaki would make a return but the injury along with how difficult the Sandame division was would be too much for Sasaki as he would only manage to be 2-5 before declaring his retirement from sumo in November 1996 at the age of 22 with an overall career record of 57-52-31.

Sasaki would then decide that he would take a risk and try and get into the sport he loved ever since he was a young kid feeling that this would be his last chance at getting into professional wrestling.

Sasaki would enter the FMW Dojo in April 1997 and would outshine everyone else in the facility being labeled the top wrestler in the dojo and would outrank future friend Naohiko Yamazaki and would also in the dojo would earn the nickname "Mammoth" for his size and strength.

FMW would feel it was time for Sasaki to be making his debut soon, but he would first participate in a exhibition match against Nobuyasu Anesaki on November 15, 1997 on an FMW show. Sasaki would get the win and it was time for him to officially to make his debut.

December 8, 1997 at the Aichi Okazaki Gym, Sasaki would finally make his debut against Koji Nakagawa in the opening match of the show and although Sasaki would lose to Nakagawa after submitting to the STF it would be the beginning of his new career as a professional wrestler. 

December 13, 1997 at the Kawasaki Club Citta, Sasaki would face off against Nakagawa again with Nakagawa making Sasaki submit to the Sharpshooter to the man that was training him in the Dojo. 

December 22, 1997 at Korakuen Hall, Sasaki would make his Korakuen Hall debut losing to Mr. Pogo # 2  in the opening match after Pogo # 2 would hit a Body Scissors on Sasaki.

January 7, 1998 at Korakuen Hall, Sasaki would face off against Super Leather for ZEN's show and would use techniques that he had learned in Sumo but Super Leather would be too big and experienced and would end up easily putting Sasaki away with a Tombstone Piledriver.

January 13, 1998 at the Shimane Izumo Dome, Sasaki's dojo friend Naohiko Yamazaki would and the the two would form a tag team as the only two rookies on the roster.

February 6, 1998 at Korakuen Hall, Sasaki and Yamazaki would team for the first time in a losing effort to Mr. Pogo # 2 and Flying Kid Ichihara after Ichihara would make Yamazaki submit to a Single Leg Crab for the win.

February 9, 1998 at the Saitama Fukaya Citizen Gym, Sasaki would pick up his first win of his career since his debut as he would defeat Naohiko Yamazaki by making him submit to a Single Leg Crab.

February 10, 1998 at the Saitama Fukaya Gaza Hall, after getting his first win of his career, Sasaki would begin a streak of facing Mr. Pogo # 2 in every opening match. Mr. Pogo # 2 who had over year of experience would be too much for Sasaki each and every time and Sasaki would go on to lose 5 straight times including a match on February 19, 1998 at Korakuen Hall.

March 13, 1998 at the Sapporo Nakajima Sports Center, Sasaki and Yamazaki would appear on their biggest show of their careers in front of an announced crowd of 4800 fans as they would open the show losing to Flying Kid Ichihara and Mr. Pogo # 2 after Ichihara would hit his Moonsault on Yamazaki for the win.

March 14, 1998 at the Ashikawa Citizen Center, Sasaki would get the opportunity to face off against former FMW Double Titles Champion Masato Tanaka for the first time in his career. Sasaki would still be way too young to even come close to scoring the major upset but would end up lasting almost ten minutes with Tanaka hitting a Flying Body Press on Sasaki for the win.

March 17, 1998 at Korakuen Hall, Sasaki would once again be put against Mr. Pogo # 2 and once again would continue to lose to him this time it would be after Pogo would make him submit to a Camel Clutch.

April 5, 1998 at the Ueno Workers Gym, Sasaki would get the opportunity to team with Hayabusa for the first time in his career as they would team up to take on Masato Tanaka and Mr. Pogo # 2 with Pogo scoring the pinfall over Sasaki after nailing him with a Pogo Bomb.

April 17, 1998 at the Sapporo Nakajima Sports Center, Sasaki would open the show up against friend and partner Naohiko Yamazaki with Sasaki getting the win to show that he was ranked above atleast one other wrestler in the company.

April 23, 1998 at the Shizuoka South Atami Marine Hall, Sasaki would score the biggest win of his career against Hido after making the freshly head shaven Hido submit to Sasaki's STF for the win which would begin a losing streak for Hido the rest of the tour.

May 19, 1998 at Korakuen Hall, Sasaki and Naohiko Yamazaki would make their PPV debuts after both being left off the first FMW PPV back on April 30th. They would appear on the second PPV by once again losing to the team of Flying Kid Ichihara and Mr. Pogo # 2 after Ichihara would hit his Moonsault on Yamazaki.

July 10, 1998 at Korakuen Hall, Sasaki, Pogo # 2, and FMW President Shoichi Arai would being in the ring making an announcement when Kodo Fuyuki would come to the ring and end up attacking Sasaki, Pogo # 2, as well as Shoichi Arai for Sasaki's first bit of direction since starting.  Sasaki would end up teaming with Mr. Pogo # 2 as they would defeat the team of former FMW young boy Mamoru Okamoto and the future Junji Tanaka in Mach Junji after Pogo would deliver a choke slam off the top turnbuckle to Junji for the win.

July 27, 1998 at the Osaka Prefectural Gym # 2, Sasaki and Mr. Pogo # 2 would look for revenge on Kodo Fuyuki for his attack from the previous week as Fuyuki would team up with Hido and Fuyuki would manage to quickly put away Pogo with a Lariat in just over three minutes.

August 11, 1998 at Korakuen Hall, Sasaki would participate in his first main event match as he would team with Atsushi Onita, Mr. Pogo # 2, and Shoichi Arai against Team No Respect's Kodo Fuyuki, Koji Nakagawa, Yukihiro Kanemura, and Go Ito in a Weapons Death Match that would have Shoichi Arai's Presidency on the line in return for Tetsuhiro Kuroda and Hideki Hosaka being let go by Team No Respect after being captive by them for the Summer. Onita would end up powerbombing Go Ito and letting Arai get the pinfall in the match to get the win and save Arai's job, and it would be the first time that Sasaki would get to team up with creator of FMW in Atsushi Onita. 

August 21, 1998 at the Kawasaki Club Citta, Sasaki would join Atsushi Onita's new group called Team Zero which would consist of Onita, Tetsuhiro Kuroda, Hideki Hosaka, and Mr. Pogo # 2. Sasaki would team with Onita and Mr. Pogo # 2 against Kodo Fuyuki, Koji Nakagawa, and Yukihiro Kanemura in the main event with Sasaki taking the fall in the match after Fuyuki would finish him off with a Lariat.

August 22, 1998 at a Tokyo TV Studio, Sasaki would take on The Gladiator in the second of three match series for The Gladiator with Sasaki being no where near the level of power and experience that The Gladiator would have as The Gladiator would finish off Sasaki with a Diving Body Press in one of The Gladiator's last matches in FMW before injuring his knee. Sasaki would eventually adapt The Gladiator's Awesome Bomb to his offense years later.

September 8, 1998 at Korakuen Hall, Sasaki would team up with fellow Team Zero member Mr. Pogo # 2 as they would end up losing to the team of the newly unmasked Super Leather and Flying Kid Ichihara with Leather finishing off Sasaki with a Slash Buster.

September 29, 1998 at the Osaka Prefectural Gym # 2, Sasaki would team up with Atsushi Onita against fellow Team Zero members Tetsuhiro Kuroda and Hideki Hosaka with Hosaka forcing the referee to stop the match on Sasaki to give the win to Kuroda and Hosaka. Also on the show, Mr. Pogo # 2 would end up losing to the original Mr. Pogo forcing him to lose his name and go by the name Gosaku instead.

November 20, 1998 at the Yokohama Bunka Gym, Sasaki would originally be scheduled to compete in a handicap match with Gosaku and Hideki Hosaka against Atsushi Onita in what would be Onita's last ever FMW match. The match would end up getting changed to Onita defeating his old rival Mr. Pogo instead. Onita would call Hosaka, Gosaku, and Sasaki to the ring to give them some words with Sasaki having to hold back tears as his leader would be leaving and ending Team Zero in FMW as a result.

December 11, 1998 at Korakuen Hall, Sasaki would make his second Korakuen Hall main event as he would team up with Atsushi Onita for the last time in over 14 years for Onita's start up USO promotion. Sasaki and Onita would take on fellow members of Team Zero in Tetsuhiro Kuroda and Hideki Hosaka in a Street Fight  with Onita getting the pinfall over Hosaka for the win and the official end to Team Zero as Onita would disassociate himself from all the members of the group after the match.

December 12, 1998 at Korakuen Hall, Sasaki would take on Hisakatsu Oya and Super Leather in a Three Way Dance and although Super Leather would end up getting eliminated by Oya first and it would come down to Oya and Sasaki it would be Sasaki submitting to Oya's Octopus Hold for the win.

January 5, 1999 at Korakuen Hall, Hideki Hosaka would break his alliance with the Team Zero group by turning on Gosaku and Sasaki after Sasaki would take the fall against Nanjyo Hayato, Flying Kid Ichihara, and Naohiko Yamazaki after Sasaki would submit to Yamazaki's Fujiwara arm bar in a humiliating loss for Sasaki. Gosaku would also end up leaving FMW shortly afterwards and Sasaki would soon become the ring assistant for Tetsuhiro Kuroda as Kuroda would begin moving up the ladder in FMW.

February 27, 1999 at Korakuen Hall, the Battlarts promotion would begin feuding with FMW and Sasaki would be put up against young Battlarts wrestler Ryuji Hijikata in the opening match as Sasaki would manage to put away Hijikata with a Chokeslam for the FMW win.

March 29, 1999 at Korakuen Hall, Sasaki would get a chance at his former Team Zero partner Hideki Hosaka who had turned on him back in January. Hosaka would begin dressing like the Big Boss Man was in WWF at the time including bringing a night stick to the ring and Hosaka would end up putting Sasaki with a running Powerbomb for the win.

April 20, 1999 at Korakuen Hall, Sasaki would face  Naohiko Yamazaki in a match that the winner would get the right to wrestle in their biggest singles match of their career as they would get to face All Japan wrestler Takeshi Morishima on May 5, 1999 at the Yokohama Bunka Gym with Sasaki getting the win with a Chokeslam over his Dojo friend.

May 5, 1999 at the Yokohama Bunka Gym, Sasaki would wrestle the biggest match of his singles career at the time as he would face off against All Japan's Takeshi Morishima in a near 10 minute match before being hit a Scrap Buster and pinned by the future NOAH GHC Champion. Following the show, Sasaki who had been aligned with Masato Tanaka and Tetsuhiro Kuroda would join up with them as they would align themselves with Hayabusa and the FMW side against Kodo Fuyuki and his Team No Respect group.

May 31, 1999 at Korakuen Hall, Sasaki would take on Nanjyo Hayato who had been a FMW regular dating back to 1994 but had left for a couple of years and was injured and about to be leaving FMW soon following due to having a bad relationship after returning. Sasaki would end up defeating Nanjyo as a result with a Chokeslam for the win.

June 15, 1999 at Korakuen Hall, Sasaki would reform his tag team with Naohiko Yamazaki against Hisakatsu Oya and Hideki Hosaka with Hosaka delivering a running Powerbomb to finish off Yamazaki for the win.

July 31, 1999 at Korakuen Hall, Sasaki would get a chance to show that he was still above Naohiko Yamazaki and would end up defeating Yamazaki in the opening match of the show with a Chokeslam.

August 20, 1999 at Korakuen Hall, Sasaki would again face off against Yamazaki in the opening match of the show and once again defeat Yamazaki with a Chokeslam.

August 23, 1999 at Korakuen Hall, Sasaki would face off against a much different opponent in the giant foreigner Giant Steele who would end up putting away Sasaki with a Chokeslam himself in just 48 seconds.

August 25, 1999 at the Sapporo Nakajima Sports Center, Sasaki would get his first ever chance at a Championship Title as he would team with Tetsuhiro Kuroda and Hisakatsu Oya and challenge for Kodo Fuyuki, Koji Nakagawa, and Gedo's WEW 6 Man Tag Team Championship which would end Gedo end up getting a Gedo Clutch on Sasaki for the pinfall as they would escape with their belts.

September 24, 1999 at Korakuen Hall, Sasaki would main event along with the team of Hayabusa going by the name H, Tetsuhiro Kuroda, and Flying Kid Ichihara against Mr. Gannosuke going by the name of Hayabusa, Koji Nakagawa, Gedo, and making his pro wrestling debut Chocoball Mukai. H would end up getting the win after hitting Gedo with the H Edge.

October 29, 1999 at Korakuen Hall, Sasaki would end up defeating Naohiko Yamazaki once again although this time they would be preparing themselves for the biggest match of their careers as they would team up to take on the legendary Funk Brothers the following month at the Yokohama Arena.

November 23, 1999 at the Yokohama Arena, Sasaki would team with Naohiko Yamazaki to wrestle in the biggest match of their careers as they took on Dory Funk, Jr. and Terry Funk at the Yokohama Arena. The end result would be Terry Funk putting Sasaki in the Spinning Toe Hold at the same time Dory putting Yamazaki in the Spinning Toe Hold with Yamazaki tapping out to Dory. Even though Sasaki and Yamazaki lost, they gained  much credibility for wrestling the legendary Funk Brothers.

January 5, 2000 at Korakuen Hall, Sasaki and Yamazaki would team with the returning from a 6 month injury Hideki Hosaka against Koji Nakagawa, Jado, and Gedo and although Jado would get the victory over Yamazaki with a Lariat in the match, a new tag of Hideki Hosaka and Yoshinori Sasaki would be soon form.

February 25, 2000 at Korakuen Hall, Sasaki would team with Hosaka in a 4 Way Tag Team match against Koji Nakagawa and Gedo, Kintaro Kanemura and Jado, and Hisakatsu Oya and Naohiko Yamazaki for the number 1 contenders for the WEW Tag Team Championship and although Sasaki would get pinned by Jado eliminating Hosaka and Sasaki from the match with Nakagawa and Gedo getting the win. Despite not winning, Sasaki and Hosaka a shot at the WEW Tag Team Titles they would be in lines for another tag team title.

March 27, 2000 at Korakuen Hall, Sasaki would team with Naohiko Yamazaki and with H subbing for Mr. Gannosuke who could not make the show against Koji Nakagawa, Jado, and Gedo for the WEW 6 Man Tag Team Championship with would end with Jado pinning Yamazaki after a Lariat. Despite the loss, it was about time that Sasaki would finally manage to break away from the undercard and become a player for FMW.

April 11, 2000 at Korakuen Hall, the push for Yoshinori Sasaki would start as he would easily defeat Flying Kid Ichihara who he had lost to so many times years earlier with a Mammoth Buster. It would be announced that on the next show that Sasaki and Hosaka would challenge for the right to become the first ever WEW Hardcore Tag Team Champions. 

April 25, 2000 at the Tokyo Shibuya Ward, Sasaki would win his first ever title in wrestling as he and Hideki Hosaka would go on to beat Kintaro Kanemura & Willie Takayama after Hosaka would hit the Grizzly Bomb on Kanemura to become the first ever WEW Hardcore Tag Team Champions. The new team of Hideki Hosaka and Yoshinori Sasaki would be scheduled to defend the titles against ECW's Balls Mahoney and New Jack on May 5, 2000 at FMW's anniversary show but that match would not end up taking place.

May 5, 2000 at the Komazawa Olympic Gym, the FMW-ECW relationship would end up coming to an end after ECW due to politics and as a result New Jack and Balls Mahoney would not show up. FMW would get The Samoans instead to  challenge for the WEW Hardcore Tag Titles with the match would turning into a bloody brawl with all four wrestlers fighting all over the building with the ending coming when Sasaki getting pin after choke slamming Fatu for the win and to walk away from the biggest show of the year for FMW still the WEW Hardcore Tag Team Champions.

May 28, 2000 at Korakuen Hall, Sasaki and Hosaka would defend their WEW Hardcore Tag Titles once again after defeating Michael Shane and Ruben Cruise after Hosaka would pin Shane. In the main event of the show, Mr. Gannosuke would defeat H and Tetsuhiro Kuroda with Kodo Fuyuki as the Special Referee. After the match, Hosaka and Sasaki would come out and turn heel on H. Sasaki and Hosaka would attack both H and Kuroda and as Kodo Fuyuki would announce his new group of Shoichi Arai, Gannosuke, GOEMON, Kyoko Inoue, Chocoball Mukai, Hideki Hosaka, and Yoshinori Sasaki which he would call the Shin Fuyuki-gun translating to the New Fuyuki Army.

June 21, 2000 at Korakuen Hall, Sasaki and Hosaka would end up dropping the WEW Hardcore Tag Team Titles to The Samoans after Samu would hit a flying body press on Sasaki in a brawl that would go all around Korakuen Hall. Fatu would hit Sasaki with a chokeslam and send him through a table to the outside of the ring. Sasaki and and Samu would end up continue brawling around ringside where as Hosaka and Fatu would brawl outside to the merchandise tables and to the balcony of Korakuen Hall where Hosaka would try to throw Fatu off the balcony but be unable to do so. Eventually after all four would make it back to ringside it would be Fatu that would end up finishing off Sasaki with a Samoan Press to get the pinfall and win the WEW Hardcore Tag Titles ending Sasaki's first ever title reign. 

July 14, 2000 in Takamatsu, Sasaki and Hosaka would get another shot for the titles, but this time Samu would get the pin over Hosaka with the Samoan Guillotine Drop to retain the WEW Hardcore Tag Titles.

July 28, 2000 at Korakuen Hall, Sasaki and Hosaka would get one more shot at The Samoans for the WEW Hardcore Tag Team Titles. All four would end up brawling all over Korakuen Hall with The Samoans with Hosaka hitting a Building Bomb to get the pinfall over Fatu with Sasaki and Hosaka winning the WEW Hardcore Tag Team Titles for the second time.

August 28, 2000 at Korakuen Hall, the team of Hosaka and Sasaki would get their biggest victory as a team defending the WEW Hardcore Tag Team Titles against Jado and Gedo after Sasaki would hit a Lariat and score the biggest pinfall of his career by pinning Jado in the match to retain the WEW Hardcore Tag Team Titles. 

Yoshinori Sasaki would then go under a name change, with his preliminary days behind him, and a new preliminary wrestler by the name of Yoshihito Sasaki debuting in FMW, it was time to change Sasaki's ring to his FMW Dojo name to Mammoth Sasaki.

September 15, 2000 at the Kumagaya Citizen Gym, Sasaki would make his debut as "Mammoth Sasaki" and take on Masato Tanaka in a match entitled "Mammoth Sasaki Renaming Commemoration Trial Series 1st" with Sasaki giving it his all to show a main event wrestler in FMW that he had what it took to be seen in that light as a main eventer but Tanaka would eventually end up hitting the Diamond Dust on Mammoth for the loss. Sasaki would get another chance just two days later.

September 17, 2000 at the Tokyo Differ Ariake, Sasaki would take on FMW's ace Hayabusa in the main event of the show as it would be named "Mammoth Sasaki Renaming Commemoration Trial Series 2nd". Sasaki would look even more impressive in this match as he would give Hayabusa all he could take including hitting Hayabusa with a chair while he was coming down from an Asai Moonsault out of the ring and chokeslamming him through a table. Hayabusa would end up defeating Sasaki in the over 24 minutes match by finishing off Sasaki with the H Thunder. Although Mammoth lost in both matches, it was very apparent that Mammoth Sasaki was climbing up the ranks in FMW.

September 21, 2000 at the Sapporo Green Dome, Mammoth and Hosaka would defend their WEW Hardcore Tag Team Titles against Jado & Gedo and Kintaro Kanemura & Ryuji Yamakawa in a Three Way Tag Team Dance when Jado and Gedo would get the win over Kintaro Kanemura & Ryuji Yamakawa after Gedo would pin Kanemura with a Thrust Kick to cost Sasaki and Hosaka their WEW Hardcore Tag Team Titles ending their second reign as champions. 

September 26, 2000 at Korakuen Hall, Mammoth and Hosaka would team up with Kintaro Kanemura to take on Masato Tanaka, Hisakatsu Oya, and Naohiko Yamazaki with Mammoth and Hosaka paying back Kanemura for being the one to get pinned in the match and lose them their WEW Hardcore Tag Team Titles as they would end up turning on Kanemura and leaving him all by himself in the match as it would allow Tanaka to easily finish off Kanemura due to the odds with with a Bullet Elbow as it now looked like the team of Mammoth Sasaki and Hideki Hosaka were on their own. 

November 12, 2000 at the Yokohama Bunka Gym, Mammoth and Hosaka would get another shot at the WEW Hardcore Tag Team Titles against the the current champions in XPW's Supreme and Homeless Jimmy on  in a brawl that would end up leaving the building as they would fight outside the building towards FMW announcer's J Taro's car. Sasaki would start off by throwing a cinder block at Supreme but Supreme would manage to move out of the way causing the block to go through the back seat window of the car. Mammoth would then bring over a table and place the table by the car and pick up Homeless Jimmy to the top of the car and deliver a choke slam off the car onto a table. They would eventually brawl back in the ring where Mammoth would end up hitting another Choke Slam on Homeless Jimmy and get the pinfall to win back the WEW Hardcore Tag Team Titles for a third and final time.

November 19, 2000 at the Aichi Port Messe, Mammoth would challenge for the WEW Hardcore Title against Kintaro Kanemura in a bloody, bloody brawl that would end up with Kanemura finishing off Mammoth after hitting him with a Powerbomb on a stack of chairs to retain his title. 

November 28, 2000 at Korakuen Hall, Mammoth and Hideki Hosaka would defend their WEW Hardcore Tag Team Titles for the first time against XPW's Supreme and Pogo the Clown. This would mark the end of the FMW and XPW relationship as Pogo the Clown would stand out in a very negative way and Supreme was not much better. Mammoth would end up hitting a Mammoth Home Run on Supreme off the top turnbuckle while Hosaka would powerbomb Supreme through a table. Hosaka would end up getting the pin after delivering a choke slam to get the pin over Supreme to successfully defend their tag team titles.

December 10, 2000 at Korakuen Hall, tension between Mammoth and Hosaka would begin as the two were going up against three young rookies in Tomokazu Morita, Yoshihito Sasaki, and Satoru Makita. Hosaka would leave Mammoth during the match out of frustration of Mammoth insisting on doing a Mammoth Home Run by placing a chair on Yoshihito Sasaki's head and then smashing it with another chair knocking Sasaki out for the win. 

December 20, 2000 at Korakuen Hall, tension between Sasaki and Hosaka would continue as Hosaka would defeat partner Mammoth Sasaki and Azusa Kudo in a triple threat match after Hosaka would pin Kudo which would angering Mammoth over Hosaka getting the win despite Mammoth not being pinned.

January 7, 2001 at Korakuen Hall, Mammoth would try to smooth things over with Hosaka before their match as Mammoth would give Hosaka a cherish childhood toy Sasaki had to show his alliance with Hosaka as they would defend their WEW Hardcore Tag Team Titles against the new team of GOEMON & Onryo. During the match, while battling all over the Korakuen Hall, Sasaki would accidentally hit Hosaka with the Mammoth Home Run knocking Hosaka out and while Mammoth would go and fight with GOEMON in the crowd and try and choke slam GOEMON through a table, Hosaka would get up and Powerbomb Sasaki through the table while GOEMON would hit a Swanton on Sasaki for the three count and the WEW Hardcore Tag Titles. Sasaki had just lost his title, his tag partner, and then Hosaka would begin to smash the childhood toy he had. 

January 16, 2001 at Korakuen Hall, Mammoth would take out his frustrations on Hosaka by destroying Chocoball Mukai and then through his friendship with Naohiko Yamazaki joining former Team Zero friend Tetsuhiro Kuroda's new group Team Kuroda which would consist of Kuroda, Yamazaki, Shinjuku Shark and Azusa Kudo.

February 6, 2001 at Korakuen Hall, Mammoth would team up with fellow Team Kuroda member Tetsuhiro Kuroda and Kyoko Inoue who had fallen in love with Kuroda and was wanting him to marry her. They would team up to take on the team of Kodo Fuyuki, GOEMON, and Onryo with Fuyuki getting the Lariat on Inoue to pick up the win. Kuroda would end up turning on Inoue for the loss and breaking her love struck heart in the process.

February 23, 2001 at Korakuen Hall, Mammoth would team up with Tetsuhiro Kuroda again as they would take on the team of Kodo Fuyuki and The Great Sasuke with Sasaki managing to pick up the win with a Small Package on Kuroda for the victory. Prior to the show it would be announced that Hideki Hosaka would be one of the wrestlers that had walked out with Masato Tanaka and left FMW due to the promotions finance problems ending any chance of a reunion of Mammoth and Hosaka in FMW.

March 5, 2001 at Korakuen Hall, Mammoth would try to win back the WEW Hardcore Tag Team Titles by teaming with Asuza Kudo against WEW Hardcore Tag Team Champions Kintaro Kanemura and Ryuji Yamakawa with Kanemura picking up the win in the bloody match by using a Backslide to get the pinfall over Kudo to defend their tag team titles. It would be the last time that Mammoth would get a chance at the WEW Hardcore Tag Team Titles for over 10 years.

March 13, 2001 at Korakuen Hall, Mammoth would team with junji.com who had last dealt with when facing him in a tag match back on July 10, 1998. Mammoth and junji.com would team up and lose to GOEMON and Onryo after Onryo would pick up the win over junji. 

April 1, 2001 at Korakuen Hall, Mammoth would score the biggest win in his career after defeating Kintaro Kanemura for the WEW Hardcore Title after several high impact moves onto a stack of chairs. Mr. Gannosuke would also join Team Kuroda and help Kuroda defeat Kodo Fuyuki for the WEW World Title as Team Kuroda would now have the two singles title in the FMW within their group.

April 15, 2001 at Korakuen Hall, Mammoth would team up with Tetsuhiro Kuroda and Mr. Gannosuke against the team of The Great Sasuke, GOEMON, and Onryo when Kuroda picking up the win for Team Kuroda by nailing Onryo with the Technan Buster for the win.

May 5, 2001 at Kawasaki Stadium, Mammoth would be making his Kawasaki Stadium debut as he would defend  his WEW Hardcore Title against an injured Kintaro Kanemura. While the match was slowed down due to Kanemura's health from injuries suffered the day before, Mammoth would hit choke slam Kanemura off the ring apron into a table and then begin to smash the table over Kanemura's head, but Kanemura would end up getting victory over Mammoth after Kanemura would hit him with a Liger Bomb to win back the WEW Hardcore title from Mammoth. 

May 11, 2001 at Korakuen Hall, Mammoth would team with fellow Team Kuroda members Tetsuhiro Kuroda and Mr. Gannosuke against Hayabusa, Hisakatsu Oya, and Ricky Fuji but due to a miscommunication spot, Gannosuke and Kuroda would run into each other and begin to argue with one another as Sasaki would try to calm them both down, which would ultimately lead to Kuroda being pinned by Hayabusa's 450 Firebird Splash.

May 22, 2001 at the Sapporo Green Dome, Mammoth would team with Mr. Gannosuke and challenge for the WEW Tag Team Titles against GOEMON & Onryo but Sasaki would end up being pinned by Onryo's Onryo Clutch to be denied the titles. After the match, Mr. Gannosuke would get on the mic and state that even though he is no longer associated with Kuroda, he wants Mammoth to be on his side and be aligned with him no matter what.

June 8, 2001 at Korakuen Hall, Kodo Fuyuki along with Stuart Levy's Tokyo Pop and FMW Vice President Senmu Yoshida announce that they plan on owning the entire FMW promotion and want all the wrestlers to leave Shoichi Arai and they would be offered plenty of money. Mr. Gannosuke, Kintaro Kanemura, Chocoball Mukai, Shinjuku Shark, and Mammoth all decide to align themselves with Fuyuki where as Hayabusa and the rest of the FMW align themselves with Shoichi Arai. Mammoth would then challenge the man who he made his debut against on December 8, 1997 in GOEMON and Sasaki would finally get his first ever pinfall victory over the former Koji Nakagawa as Mammoth first smash GOEMON's head while laying on the ring post with a chair and then finish GOEMON off with the Mammoth Home Run to totally knock out GOEMON for the victory for Mammoth. 

July 2, 2001 at Korakuen Hall, Mammoth would face off against his former leader and partner Tetsuhiro Kuroda as Kuroda would still be just be too experienced for Mammoth and would end up finishing off Mammoth with a Lariat for the win despite Mammoth moving up the card to a main event wrestler.

July 20, 2001 at Korakuen Hall, Mammoth would then be aligned with Senmu Yoshida with Yoshida acting as his manager. Mammoth would go on to feud with Onryo and ultimately get a singles victory over Onryo which would earn Mammoth a chance at his first ever World Title shot.

July 30, 2001 at the Fukuoka Hakata Star Lanes, Mammoth would challenge for Hayabusa's WEW World Title. Despite having having Mr. Gannosuke, Kintaro Kanemura, and the rest of the Tokyo Pop faction it would still end up Mammoth taking the fall in a long battle after Hayabusa would deliver a Fire Bird Splash off a table placed on the top turnbuckle to defend his title for the first time.  

August 11, 2001 at the Komazawa Olympic Gym, Mammoth would then team with Chocoball Mukai to again challenge for GOEMON and Onryo for their WEW Tag Team Titles in a Octagon Cage Match, but again Mammoth would not walk away with the titles as Onryo would end up rolling Mukai up for the Onryo Clutch for the win to defend their titles.. 

September 5, 2001 at the Sapporo Green Dome, in a rematch in the same building for the WEW Tag Team Titles, Mammoth would again team with Mr. Gannosuke to challenge for GOEMON and Onryo for the WEW Tag Team Titles and Mammoth would finally win the WEW Tag Titles from them after pinning Onryo to get the win for the WEW Tag Team Titles.

September 9, 2001 at Korakuen Hall, even though Mammoth had graduated from the FMW Dojo years ago, he still helped out and trained and lived in the Dojo to help the upcoming wrestlers out, one of those wrestlers was Yoshihito Sasaki and Yoshihito would be given a big shot to defeat his superior in Mammoth .Sasaki. Yoshihito would attempt the entire match for the Canadian Backbreaker, but Mammoth's size would be too much until finally Yoshihito would put Mammoth on his shoulders and drop him down to the mat, but only getting a two count. Mammoth would power his away and get the win. 

October 9, 2001 at Korakuen Hall, Mammoth would team up with Mr. Gannosuke as they would defend their WEW Tag Team Titles against Hayabusa and Tetsuhiro Kuroda. Mammoth and Gannosuke would end up losing their WEW Tag Team Titles after Hayabusa would end up rolling up Mammoth for the win and the WEW Tag Team Titles. Senmu Yoshida would announce that Mammoth would face off against Hayabusa in a singles match at the next Korakuen Hall show and if Hayabusa were to get the win than Shoichi Arai would return as President of FMW. 

October 13, 2001 at the Osaka Prefectural Gym # 2, Mammoth would team up with Kintaro Kanemura, Mr. Gannosuke, and NOSAWA against the team of Hayabusa, GOEMON, Onryo, and Hisakatsu Oya in a Single Elimination Match. It would come down to Mammoth and Hayabusa as the last two competing for their teams when Mammoth would end up nailing a Super Chokeslam off the top turnbuckle on Hayabusa to score his first ever pinfall over Hayabusa and get the win for his team.

October 22, 2001 at Korakuen Hall, Mammoth Sasaki would face Hayabusa in his first single main event at Korakuen Hall. Mammoth would be in control for a majority of the match hitting many of his power moves, but Hayabusa would soon take charge and begin to hit his signature spots. Hayabusa would then begin to deliver his signature Asai Moonsault in the ring when his foot would slip on the rope causing himself to land head first and become instantly paralyzed. Hayabusa not knowing the extent of the damage would tell FMW referee Marty Asano for the match to keep going, as Mammoth would begin to do what he was told and keep going and stomp on Hayabusa and then put him in a chin lock before the referee would finally call for the match to end. Mammoth would watch as many of the babyface wrestlers would come into the ring to see what had happened to Hayabusa. They would begin to put Hayabusa on a stretcher when Kanemura would head to the ring and get Mammoth out and head to the back as Hayabusa would be taken to an ambulance and be taken to the hospital.

November 23, 2001 at the Yokohama Bunka Gym, due to Hayabusa's injury the WEW Tag Team Titles would be vacated and Sasaki would team with Mr. Gannosuke to take on Biomonster DNA and Dr. Luther for the vacant belts. Gannosuke would end up scoring the pin on Luther as the team of the Mr. Gannosuke and Mammoth Sasaki would score their second WEW Tag Titles, but would end up vacating the titles. After the main event, due to Kodo Fuyuki joining the WAR team, a disgusted Sasaki, Gannosuke, Kanemura along with Kuroda would enter the ring with Gannosuke having to be held back by  Koki Kitahara from attacking Tenryu while Kanemura would attack Fuyuki with Fuyuki making a run from it. Gannosuke would grab the microphone and declare a war between FMW and WAR with Kanemura, Mammoth, and then Kuroda joining along side Gannosuke in the fight against Tenryu's WAR.

December 9, 2001 at Korakuen Hall, the FMW team of Mammoth Sasaki, Tetsuhiro Kuroda, Kintaro Kanemura, and Mr. Gannosuke would take on the WAR team of Genichiro Tenryu, Kodo Fuyuki, Arashi, and Koki Kitahara with all the members of Team FMW working on Tenryu and getting him off his feet and all four of them hitting power move on Tenryu when then Mr. Gannosuke with get a Gannosuke Clutch on Kodo Fuyuki giving Team FMW the last win in the battle against Team WAR as Mammoth would hold up Hayabusa's mask in Eiji Ezaki's honor to end the show. 

December 21, 2001 at Korakuen Hall, Mammoth Sasaki would then enter the WEW Tag Team Tournament with Kintaro Kanemura in a one night tournament. Before the tournament, Dojo friend Naohiko Yamazaki would have his retirement match due to an eye injury he had suffered, and afterwards Mammoth would hand Yamazaki flowers and wish his good friend luck for the future. Then in the tournament,  Sasaki and Kanemura would first defeat the team of Horace Boulder and Balls Mahoney after Mammoth would hit a Mammoth Home Run on Horace Boulder and then getting the pin to advance to the semi finals where they would face Super Crazy and Crazy Boy and would advance to the finals after Mammoth would hit a Mammoth Home Run on Crazy Boy while Crazy Boy was on Kanemura's shoulder and Kanemura would then hit a supplex to get to the pin and take on Tetsuhiro Kuroda and Mr. Gannosuke in the finals. In a bloody match, Mammoth would end up falling after being hit with a Technan Buster by Kuroda to give the win to Kuroda & Gannosuke. The four would shake hands afterwards and would have to be prepared for what Kodo Fuyuki was about to do. 

January 6, 2002 at Korakuen Hall, Mammoth would team with Tetsuhiro Kuroda and Mr. Gannosuke to take on the new foreign team brought in by Kodo Fuyuki of The Sandman, Vic Grimes, and The Sandman, it would turn into a handicap match after Mr. Gannosuke was set on a table, and Vic Grimes dive off the turnbuckle to the outside where Gannosuke was laying on the table, Gannosuke would quickly roll off the table but his foot would end up still being under the table as Grimes 400 pound body would come crashing down on Gannosuke's leg which would result in Gannosuke being carried off to the back and which would lead to Vic Grimes scoring the pinfall over Mammoth Sasaki.

February 4, 2002 at Korakuen Hall, in what would turn out to be the last ever FMW show, Mammoth Sasaki would team with Kintaro Kanemura and GOEMON against Vic Grimes, Paul LeDuc, and Mitsunobu Kikuzawa in another hardcore match in which GOEMON was beaten to a pulp the entire match and incredibly bloody before Mammoth would end up scoring the pinfall over Kikuzawa in his last ever FMW match. After the main event, Mammoth would come out and announce that he would be participating at PRIDE's February 22nd Korakuen Hall show and would leave not knowing that would be the last time he ever step into a FMW ring. 

Mammoth would end up getting his paycheck but would end finding out that the check had bounced. Shortly after that it would be officially announced on February 15, 2002 that FMW had officially declared bankruptcy and was two million dollars in debt. Kodo Fuyuki would announce to the FMW wrestlers that he was plan on running the FMW shows that were for March 10, 2002 show under his name and would start his own promotion with the help from the FMW wrestlers. Mammoth along with GOEMON would end up several days later officially closing down the FMW Dojo, the Dojo for over 10 years had helped trained wrestlers from Hayabusa to Mr. Gannosuke to Masato Tanaka to Koji Nakagawa to Mammoth Sasaki.

February 22, 2002 at Korakuen Hall, Mammoth would have his tryout match for new PRIDE fighters with Mammoth hoping that he would be able to maybe catch on to a very profitable promotion in PRIDE but Mammoth would end up just not prepared for such a different kind of style match as he would end up being knocked out by former Pancrease fighter Kim Jong Wan in 25 seconds. Mammoth would shortly announce after the embarrassing lost that he would be retiring from shoot fighting. 

March 10, 2002 at Korakuen Hall at Kodo Fuyuki's promoted show, Mammoth would team with GOEMON & Onryo to defeat the team of Biomonster DNA, NOSAWA, and Chocoball Mukai with Mammoth getting the pinfall over NOSAWA but Mammoth would get very angry at Kodo Fuyuki as Atsushi Onita would appear at the show while Fuyuki was giving a 10 bell salute to FMW. Mammoth who still had bitter feelings about Onita after leaving FMW when the promotion needed him in 1998 with Onita taking his ball and going home showed very much frustration with Fuyuki for having Onita come in like this would work two more of Fuyuki's promoted shows before bailing out, soon after Fuyuki would also lose GOEMON, Onryo, and Flying Kid Ichihara in the next upcoming weeks. Mammoth would sit at home for the next several months while the secret that just the FMW wrestlers knew was being put together piece by piece.

July 3, 2002 in a Tokyo Press Conference, with former FMW wrestlers GOEMON, Onryo, Flying Kid Ichihara, Mr. Gannosuke, Garuda, Satoru Makita, Happy Ikeda and Mammoth Sasaki would all accompany Hayabusa in his wheel chair to announce the beginning of the new promotion "WMF" which would begin on August 28, 2002 and would hope to carry on the FMW name and tradition.

August 28, 2002 at Tokyo Differ Ariake at the WMF debut show would wrestle in the main event against Garuda with Mammoth coming out to a new techno version of the old FMW song as well as FMW t-shirt which he would take off to reveal a WMF t-shirt. Mammoth would keep the match together with Garuda showing signs of potential, but also being green, and Mammoth would do a very good job of putting the match together and making it work between the two, and would end up kicking out Garuda's 450 Firebird Splash at a one count and then finishing Garuda off the Mammoth Buster for the win. Mammoth would shake Garuda's hand and hug as the two of the wrestlers that what the WMF is based off as the future of wrestling.

September 16, 2002 at the Tokyo Shinjuku Island Hall, Mammoth would face Hisakatsu Oya but would be attacked by Mitsuhiro Matsunaga and his barbed wire baseball bat during the match due to both Mammoth and Gannosuke getting very vocal at Matsunaga about not being allowed in the WMF. Matsunaga would knock Mammoth out with the bat and set up the easy win for Oya as the referee would stop the match due to Mammoth's condition. Mammoth would ask Mr. Gannosuke who had taken duties as commissioner for the show from Hayabusa and begged Gannosuke for a match at the next WMF show against Mitsuhiro Matsunaga in a match where if Matsunaga won, then he and death matches would be accepted in the WMF, but if he lost, he would have to leave WMF for good.

September 29, 2002 at the  Saitama Koshigaya Katsura Studio, Mammoth would face Matsunaga who would be wrestling his karate outfit which he used in the early 90's as a pro wrestler, and Mammoth would end up quickly finishing the karate style Matsunaga in just over 5 minutes after hitting the Mammoth Buster on Matsunaga for the win getting rid of Matsunaga from WMF. 

October 6, 2002 at the Nagoya Bicycle Race Track, while teaming with Flying Kid Ichihara against Garuda and Flying Kid Ichihara, Mammoth would fracture his fibula and as a result would be out for over 2 months with a cast on his leg., his return match would be scheduled for December 12, 2002 against Tetsuhiro Kuroda at WMF's Korakuen Hall show.

October 15, 2002 at the Tokyo Kitazawa Town Hall, Mammoth in a cast on his leg would come to the ring and announce to the crowd that he would not be able to wrestle on the show like originally announced and that he was very for being unable to compete. Mammoth would leave the ring, but when heading to the back would be met up with Brand Double Cross' GOEMON, Hisakatsu Oya and Tetsuhiro Kuroda who would attack Mammoth by going after the injured leg. Brand Double Cross would leave Mammoth lying on the ground screaming in pain as they would laugh and walk off.

December 12, 2002 at Korakuen Hall, Mammoth would return to the ring for the first time since he suffered his fractured fibula two months before, as well as return to Korakuen Hall for the first time since March 10th to do battle against former friend Tetsuhiro Kuroda in the main event of WMF's first ever Korakuen Hall show. Mammoth and Kuroda would go right at it with Kuroda landing his lariats on Mammoth where as Mammoth would hit Kuroda with his power moves including choke slamming Kuroda from the apron through a table, afterwards pieces of the broken table would come into play as both would bust each other up with the pieces of table, and then chairs would get involved with Mammoth going for his Mammoth Home Run on Kuroda, and in the end, the two both knocked out from all the chair shots and table shots with one last breath would attempt to knock each other out and in the end result, both would collapse and the referee would count to 10 and call for the match as it would end in a Double KO. Both Garuda and Onryo would come out to help their fellow WMF partner as Mammoth's cut from the head could be covered up. Mammoth would grab the mic and thank the fans for showing up and would acknowledged his respect for Kuroda after their bloody battle.

December 21, 2002 at the Sapporo Teisen Hall, Mammoth would wrestle Garuda in a rematch from the WMF debut show. Mammoth would get the win over his friend with an avalanche choke slam for the finish. After the match, Mr. Gannosuke who had turned on Jinsei Shinzaki earlier would attack Mammoth as Tetsuhiro Kuroda would come out and make the save for Mammoth, by going after Gannosuke and getting him out of the ring. Mammoth would then grab the mic and thank Kuroda for making the save as the two would shake hands, and then Mammoth would make a challenge to Mr. Gannosuke for a future battle in 2003. 

January 12, 2003 at the Tokyo Takenotsuka Battle Sphere, Mammoth Sasaki would open up the new year by teaming with Tetsuhiro Kuroda and Garuda to take on Brand Double Cross' GOEMON, Soldier, and their newest member Mr. Gannosuke. The rivalry would start between the former WEW Tag Team Champions by Gannosuke pinning Mammoth with a Gannosuke Clutch to start the new year with a win for Brand Double Cross.

February 15, 2003 at the Osaka Sky Dome Hall, Mammoth would get revenge on Brand Double Cross when teaming with Michinoku Pro's Jinsei Shinzaki to take on Mr. Gannosuke wrestling as Hayabusa and Hisakatsu Oya wrestling as HISAKATSU. Mammoth would finish off HISAKATSU with a lariat for the pin. Afterwards, Hayabusa and HISAKATSU would begin shoving one another for the loss, causing Gannosuke to retire the Hayabusa gimmick of his once again and return as Mr. Gannosuke and leave Brand Double Cross to form his own group, The Guns. Mammoth would give a speech to the crowd talking about it being the 1 year anniversary of FMW's bankruptcy, that as the ace of WMF, that he wants to help WMF thrive far into the future.

March 9, 2003 at the Tokyo Takenotsuka Battle Sphere, Mammoth would defeat Asian Cougar and afterwards, Hayabusa went get on the mic and announce that Mammoth would be facing off in the main event at the next WMF Korakuen Hall show on April 11th, against Masato Tanaka which would get a huge pop from the crowd. Mammoth would tell everyone that he would train hard to be ready against the former FMW star.

FMW booker and wrestler Kodo Fuyuki would pass away on March 19, 2003 in a Yokohama Hospital due to cancer. Mammoth along with many of the WMF wrestlers would attend the wake for Fuyuki on March 23rd to say goodbye to their former friend, and boss Kodo Fuyuki. 

April 11, 2003 at Korakuen Hall, Mammoth would face Zero-One's Masato Tanaka in Tanaka's WMF debut. Mammoth who debuted the name Mammoth Sasaki against Masato Tanaka in FMW back on September 15, 2000 would go to the ring to prove a point to Tanaka at his improvement in the near 3 years since their last singles match. The two would start off by exchanging chops between one another. Mammoth would give it to Tanaka by supplexing Tanaka several times on his head, choke lamming him, and hitting a Mammoth Home Run as well as the Mammoth Driver but still could not get the pin. Tanaka would come back with his signature offense which would include a Reverse DDT off the top rope sending Mammoth face first into the mat, and finally finish Mammoth off with several rolling elbow smashes causing Mammoth to looked incredibly dazed before Tanaka could get him off his feet with another Rolling Elbow Smash for the cover for the victory for Masato Tanaka in one of the best matches in WMF & Mammoth's career as the two put on a fantastic match. Tanaka afterwards would get on the mic and congratulate Mammoth on such a performance, that he has came along way since his earlier days and believes Mammoth will make a very good ace for WMF. Mammoth would reply by showing the respect to Tanaka as the two would then shake the hands of the fans around ringside together to end the show.

May 23, 2003 at the Osaka Sky Dome Hall, Mammoth Sasaki would finally get to face off against Mr. Gannosuke in a singles match. Atsushi Onita would appear during the match, and attack Mr. Gannosuke who was set to face him in a match the next day at a Onita Pro show. Onita's attack on Gannosuke would be enough for Mammoth would score the biggest win of his career by pinning Gannosuke with a lariat. Despite the crowd going crazy for the Onita appearance, the match would still be considered too short and a disappointment, but Mammoth Sasaki would establish himself as the top guy in the promotion by defeating Gannosuke. Gannosuke would not take to kind to the defeat of Mammoth, and would get his revenge eventually. 

July 7, 2003 at Korakuen Hall, Go Ito would take over Kodo Fuyuki's WEW promotion with it being renamed Fuyuki Army Promotion. Go Ito and Hayabusa would work together, with the first show being a FMW reunion show at Korakuen Hall. Mammoth Sasaki would team with Mr. Gannosuke despite their differences as well as TAKA Michinoku against Genichiro Tenryu, Kintaro Kanemura, and Masao Orihara. Mammoth would go after Kanemura most of the match, which included choke slamming him through a table, and nailing him with a Mammoth Driver. Both he and Gannosuke would go to throw Kanemura into the turnbuckle, but instead Gannosuke would turn on Mammoth and grab him by the hair and nail him with a clothesline and leave Mammoth to be attacked by Tenryu and then finished with a Kanemura Senton splash to pin Mammoth. Afterwards, Tenryu would pour water onto Mammoth and the two would form a friendship as Mammoth would help accompany Tenryu to the ring for the World Japan July 20th show. 

Mammoth would agree to team with Tetsuhiro Kuroda to get revenge on Mr. Gannosuke with his partner being Atsushi Onita at the July 25th WMF Korakuen Hall show. The problem would be that just hours before the show, Onita would get called into an emergency Japanese Diet meeting. The match would be reshuffled at the last moment, and instead the main event would turn into Mammoth Sasaki & Tetsuhiro Kuroda & a Mystery Partner taking on Mr. Gannosuke along with his GUN members Mr. Rocknosuke and Mr. Iwaonosuke. 

July 25, 2003 at Korakuen Hall, due to Onita's emergency meeting, the show would be the poorest attended WMF Korakuen Hall show by far. Mammoth Sasaki would reveal his mystery partner to be Kintaro Kanemura making his WMF debut in a Street Fight against The GUN's. The stipulation of the match, that if Mammoth's team lost, then WMF would officially end. Although nowhere near the quality of match that Mammoth had the first two Korakuen Hall shows, Mammoth would get his first WMF Korakuen Hall win after pinning Mr. Iwaonosuke with the debut of his new finisher The 29 Years Old to keep WMF from officially ending. Afterwards, Mammoth would announce that he would be participating for the World Japan Promotion.

July 31, 2003 at Funabashi City Gym, Mammoth would make his debut by losing to Masamitsu Kochi after an inside cradle, and then the next day on August 1st would lose to Shiro Koshinaka after being nailed with a Powerbomb. 

August 21, 2003 at the Osaka Prefectural Gym, Mammoth Sasaki would get his first World Japan victory by defeating Kuniyoshi Wada with a camel clutch to setup his biggest World Japan match on August 23, 2003 at the Fukouka Hakata Star Lanes by teaming with Takao Omori and facing off against Riki Choshu & Shiro Koshinaka as Mammoth would be pinned by Choshu after a lariat in the match. 

August 25, 2003 at Korakuen Hall, Mammoth Sasaki would be originally scheduled to team with Tetsuhiro Kuroda to take on Masato Tanaka & Yoshihito Sasaki. But instead, Mammoth would be moved back down the card and team with K-Dojo member MIYAWAKI to take on GOEMON & Onryo. Mammoth would get the pinfall victory over GOEMON, but it would become quite obvious that Fuyuki Army booker Go Ito did not have the confidence in Mammoth as Hayabusa & WMF had by having him work undercard matches in Fuyuki Army while main eventing in WMF. Later on the show, Kintaro Kanemura would defeat Mr. Gannosuke in the main event, and after Kanemura would get on the mic and issue an invitation with Mr. Gannosuke and the other wrestlers on the show to group together to declare war on Zero One as the Apache Army. 

September 6, 2003 at the Tokyo Differ Ariake, Mammoth Sasaki would team with Tetsuhiro Kuroda & Ikeda-kun to take on Mr. Gannosuke, Kintaro Kanemura, and Hido at WMF's 1 Year Anniversary show. Ikeda-kun would be taunted before the match by Gannosuke & Kanemura for being such a weak link to the team, as Ikeda would try his hardest and show his fighting spirit before eventually being pinned by Gannosuke. Mammoth would embrace Ikeda-kun as the two would remain one of the few WMF members not in the Apache Army.

September 22, 2003 at Korakuen Hall, Mammoth Sasaki would team with YOSHIYA, MIYAWAKI, and Ikeda-kun against TAKA Michinoku, Takashi Sasaki, GOEMON, and Onryo in another one of Mammoth's midcard matches in Fuyuki Army as TAKA would make Ikeda-kun tap to the Just Face Lock. After Ikeda-kun would declare that he would be making a chance, and would no longer just be a comedy wrestler. 

September 23, 2003 at the Saitama Pepe Hall Atlas, Mammoth would face Ikeda-kun going by his real name Seiji Ikeda in the main event. Ikeda would show his serious side and bring a good contest and show his fighting side, before eventually nailing the 29 Years Old on Ikeda for the win as Mammoth would shake Ikeda's hand for putting on such a performance in the match. 

October 19, 2003 at the Tokyo Differ Ariake, Mammoth would face off against Hido in the first ever WMF Death Match. Caribbean Barbed wire Board Ladder match with certain mystery bags with an object held above the ring. Mammoth would come to the ring with chairs, but Hido would come to the ring with Florescent Light sticks. Mammoth would grab one of the bags first, and pull out a fan, but Mammoth would still use it as a weapon by throwing Hido into the ropes and then hitting Hido with the fan as he came back. Mr. Gannosuke would eventually run to the ring and attack Mammoth as Hido would grab one of the bags to reveal handcuffs. Gannosuke would handcuff Mammoth as Hido would smash a Fluorescent Light Tubes over Mammoth's head to get the pin on Mammoth. Garuda would come out and make the save for Mammoth afterwards. Mammoth would meet up with Hayabusa and ask for a match at Korakuen Hall on November 20th for the right to face Mr. Gannosuke and Hido, with his partner being Genichiro Tenryu returning as his Hayabusa gimmick for the first time since FMW in June 2000. 

November 20, 2003 at Korakuen Hall, Mammoth would team with Tenryu as Hayabusa against Gannosuke and Hido in a Street Fight. Mammoth would brawl with Hido during the match in the ring as Gannosuke and Hayabusa would brawl into the crowd. Eventually, Hido would bring out his barbed wire bat against Mammoth but Hayabusa would end up capturing the barbed wire bat and using it on Gannosuke and Hido. Gannosuke and Hido would get the upper hand and pull off the Hayabusa mask of Tenryu's and would both receive hard Tenryu slaps for it. Tenryu and Gannosuke would again brawl around ringside as Mammoth would make the come back on Hido and finish him off with the 29 Years Old for the pin. Mammoth afterwards would make a challenge to Tenryu for the next WMF Korakuen Hall show on December 27th in a singles match.

December 5, 2003 at Korakuen Hall, Kintaro Kanemura would pull out before the show due to injury to his mouth and would have to take an emergency meeting the hospital. Apache Army of Tetsuhiro Kuroda & Mr. Gannosuke would announced they would have a Mystery Partner against the Zero-One team of Shinjiro Otani, Masato Tanaka, and Tatsuhito Takaiwa in a War Games Match. Mammoth would finally be able to get the push in a main event match at a Fuyuki Army show as he would turn out to be the mystery man and the newest member of the Apache Army as his music would play to a huge pop while he came to the ring the same time Shinjiro Otani would. Mammoth would begin throwing tons of chairs from the crowd into the ring as he would climb up and be met by Masato Tanaka as the two would begin brawling up on top of the cage. Mammoth would eventually get to the ring and grab the barbed wire bat that was lifted up above the ring. Only getting to use it once before Mammoth would get knocked down and the bat would end up in Otani's hands. Mammoth and Takaiwa would begin brawling on top of the cage as Mammoth would attempt to climb up it to get out of the cage to bring more weapons. Both of them would end up fighting each other to the outside and brawling into the crowd as Mammoth would end up getting a table into the caged ring. The table would end up being smashed after Big Japan's Ryuji Ito would come out to help the Apache Army by jumping off the cage and sending Otani through the table. Mammoth would end up getting back in the ring and even hitting a Mammoth Home Run on Tanaka, but with Gannosuke handcuffed, and Kuroda extremely bloody, the Apache Army would end up taking the loss after Otani would hit Kuroda with a Spiral Bomb for the win for Zero-One. Afterwards, Gannosuke and Mammoth would put the end of their rivalry by shaking hands with one another.

December 27, 2003 at Korakuen Hall, Mammoth would fight in the biggest singles match of his career against the man that had been his mentor throughout the last half of the year in Genichiro Tenryu. Mammoth would stand up to Tenryu and exchange chops between one another. Mammoth would take a big risk by slapping Tenryu in the face, causing Tenryu to go off, but Mammoth would manage to hold his own. Tenryu would gain the advantage doing that and begin working on Mammoth's knee before Mammoth would send the match outside and try and turn into a brawl with Tenryu. Tenryu would a beer bottle and smash it over Mammoth's head. Mammoth would manage to make a come back and try to finish off Tenryu with his Mammoth Home Run as he would place the chair over Tenryu's head and swing it at his head with a chair as hard as possible, but still could not finish Tenryu off. Mammoth would then hit his 29 Year old finisher patterned after Tenryu, but would still fail to put Tenryu away. Eventually Tenryu would get the upper hand on his pupil and finish him off with his 53 Year Old finisher and get the pinfall over Mammoth. Tenryu afterwards would show his respect to Mammoth for a well put performance between the two. Seiji Ikeda, GOEMON, and Onryo, as well as Mr. Gannosuke would come out to poor water over Mammoth as well as spray his neck. Gannosuke who had feuded with Mammoth throughout the entire year in WMF would show their differences were over as he would embrace Mammoth and hug him to end the show. 

January 12, 2004 at the Saitama Pepe Hall Atlas, Mammoth would start off 2004 in a new feud as after he would put away WMF youngster Mineo Fujita with the 29 years old, both would be attacked by DDT's Tomohiko Hashimoto and Seiya Morohashi who had declared war on WMF after the match. Hashimoto and Morohashi would not be done as they would attack Onryo and WMF President Yoshida afterwards before Mammoth would come back out and begin brawling with them all over the arena, as the WMF vs. DDT feud was now on. 

WMF would reveal bad news on January 23, 2004 that no show has been booked past February 11th at Korakuen Hall, and that it looks like that WMF's short life would be ending after the show. Mr. Gannosuke would be given the spot as the main WMF guy for the possible last show as he would face former IWGP Heavyweight Champion Kensuke Sasaki in the main event, and Mammoth would be put with Mineo Fujita to continue the feud with DDT's Tomohiko Hashimoto & Seiya Morohashi. 

February 11, 2004 at Korakuen Hall, Mammoth would be able to hold his own against the DDT's Tomohiko Hashimoto and Seiya Morohashi, but Mineo Fujita wouldn't be able to hold his own in the ring against the much larger wrestlers. Mammoth would turn the match into a brawl outside, throwing and swinging chairs at the DDT wrestlers, but when the DDT wrestlers would get a hold of Fujita, they would make short work of him be delivering a top rope suplex on Fujita with Morohashi grabbing Hashimoto while suplexing Fujita. Hashimoto would then finish off Fujita with the XCT and get the pin for DDT over WMF. After the match, Hashimoto would challenge Mammoth to a singles match at a DDT show as their feud as the WMF vs. DDT feud was not over. In the main event, Kensuke Sasaki would defeat Mr. Gannosuke in a bloody match. Mr. Gannosuke would call in all the WMF wrestlers to the ring and announce that this was not the final show for WMF like most people thought, but that it was the end of Stage 1 for WMF. The promotion would be closing for 6 months and restarting in August. In the mean time, Mammoth and Gannosuke would continue working Fuyuki Army Promotion shows. Mammoth and Gannosuke would embrace and hug at the end of the show.

February 12, 2004 at Korakuen Hall, Mammoth would team with fellow Apache Army member Hido to face Ryuji Ito and MIYAWAKI in a Barbwire Board Scramble Bunkhouse Match. MIYAWAKI would get busted open by Mammoth during the match, but payback Mammoth by being able to escape Mammoth's Home Run and turning it around and placing a chair over Mammoth's head and swinging for the fences on the chair and laying out Mammoth with his own move. Mammoth dazed and confused would still manage to keep going during the match, and stay effective by delivering a running powerbomb to Ito through the barbwire board slicing his back even more up. Hido would then finish the job by taking a barbwire bat and piledriving Ryuji Ito's through it and score the victory for the Apache Army as a result.

March 19, 2004 at Korakuen Hall, the show would be a Memorial to the one year anniversary of Kodo Fuyuki's passing. Every wrestler on the show would bring yellow flowers to the ring in memoriam for Fuyuki before the show. Mammoth would face off against former FMW wrestler Chocoball Mukai for a series of Chocoball's trial matches. The match would start right away as a brawl with both wrestlers swinging chairs outside the ring at one another, with both getting their shots in at one another hard to the head. Mukai would come close to scoring upset, as out of nowhere he would deliver the Sampson Clutch rollup on Mammoth and almost manage to get the three count. But Mammoth would be too much for Mukai and deliver the enziguri and finish off Mukai with the 29 Years Old for the victory. Afterwards, Mammoth would show his respect Chocoball by raising his hand after the match.

Mammoth would then be booked for a match with Masato Tanaka after Tanaka had came to odds with fellow Zero One wrestlers Shinjiro Otani and Tatsuhito Takaiwa for the Fuyuki Army Promotion May 5th Kawasaki show, which would also be the last Fuyuki Army Promotion show due to Kaoru Fuyuki backing out of her former husband's business. The show would go through many booking changes throughout the days going into it, with both Shinya Hashimoto and Riki Choshu not announcing their intention for the show until a week before it. Shinya Hashimoto would get moved from the main event to face Mammoth Sasaki, in one of Mammoth's biggest matches of his career for the show. But first, he would have to settle scores with another Hashimoto.

May 3, 2004 at Korakuen Hall, Mammoth would face off against Tomohiko Hashimoto in DDT in a match that would be off a little in a match that would be considered so-so. Mammoth would have his problems during the match, as he would chokeslam Hashimoto off the apron through a table, with Hashimoto just barely hitting the table. Mammoth would deliver his Mammoth Home Run, and then finish off Hashimoto with the 29 Years Old for the victory. After the match, the WMF vs. DDT would be put to rest as Mammoth and Hashimoto would shake hands in a show of respect for one another.

May 5, 2004 at Kawasaki Stadium, it would be the second time that Mammoth would be wrestling in the area that saw so many legendary FMW matches, and the first since his match against Kintaro Kanemura in 2001. Mammoth just two days after defeating Tomohiko Hashimoto, would now face the much more legendary Shinya Hashimoto. Mammoth would start off the match going after Hashimoto's well known injured shoulder with clotheslines to it, but Hashimoto would go after Mammoth with hard kicks of his to Mammoth's legs. Mammoth would manage to knock Hashimoto to his feet with clotheslines, and bring in a chair and go right away for the Mammoth Home Run on Hashimoto and deliver it, but Hashimoto would not sell much of the devastating move and begin stiff kicking Mammoth in the face and chest before delivering a DDT to Mammoth and bring the match to the mat. Hashimoto would place a Triangle Choke on Mammoth and the pain would become too much for the referee to watch Mammoth suffer as he would call for the bell and reward the match to Shinya Hashimoto via Referee Stoppage. Mammoth would show sportsmanship to Hashimoto and shake his hand for a well fought match.  Afterwards, a very emotional Mammoth would be interviewed backstage of the show and begin to break down in tears after the match and the whole situation that has taken place with both WMF and Fuyuki Army being in poor situations with a bleak future. 

Afterwards, Mammoth would join the other former FMW wrestlers and begin touring in World Japan against Riki Choshu and his group of Indy hating wrestlers. Mammoth would face off against Yoshiaki Fujiwara, but would not fair well once again in World Japan like he did the year before with Riki Choshu as the booker as Fujiwara would manage to defeat Mammoth with his Fujiwara Armbar on June 19, 2004. Mammoth would follow up with a victory the next day over Kazuhiko Matsuzaki, but would take the fall on June 21, 2004 teaming with Mr. Gannosuke to face Shiro Koshinaka and Takao Omori when Omori would pin Mammoth with a lariat for the victory for the World Japan team. After the show, the WMF and Apache Army would split as differences between Gannosuke and Kanemura would cause the WMF wrestlers go back to doing their own shows when the promotion would start back up, and Kanemura's Apache Army continuing to feud with Riki Choshu's World Japan without help from his former FMW friends.

August 7, 2004 at the Tokyo Kitazawa Hall, WMF would return for the first time in nearly 6 months to a sell out show in front of a small audience, with the promotion only booking in much smaller arenas due to lack of funding. Mammoth's respect towards DDT's Tomohiko Hashimoto would spawn a tag team for the show, as they would team up to face Onryo and Pennsylvania's IWC Super Hentai. Mammoth would be able to score the victory over Hentai using the 29 Years Old to finish off the foreigner. 

August 29, 2004 at the Saitama Pepe Hall Atlas, Mammoth would once again team with Tomohiko Hashimoto, as well as his partner Seiya Morohashi to face against the team of GOEMON, Onryo, and Junji Tanaka for WMF's 2nd Year Anniversary show, and once again Mammoth be able to win one for his team as he would manage to pin Junji using the 29 Years Old for the win.

WMF would then announce an 8 man Round Robin Tournament pitting the 8 WMF wrestlers in matches against each other for over three months starting in November. Mammoth Sasaki, Mr. Gannosuke, GOEMON, Onryo, Garuda, Soldier, Seiji Ikeda, and Mineo Fujita would all be entering and facing each other for the right to WMF whatever idea for a future match that you would want. Mammoth along with Mr. Gannosuke would be predicted as the top two to advance and face each other in the finals of the tournament.

November 6, 2004 at the Tokyo Takenotsuka Battle Sphere, Mammoth would first face off against Soldier, and although Mammoth would be able to score the victory over Soldier in the best match of the show to gain him two points, it would not come without its consequences, as Mammoth would severely injure his knee during the match and would announce that he would not be ready for another match later in the month against Garuda, and as a result would have to forfeit the match to Garuda. Despite the bad news of his injury, good news from the tournament for Mammoth would be that other favorite Mr. Gannosuke had lost his first two matches to Soldier and Seiji Ikeda and was the only wrestler in the tournament to not have any points.

December 18, 2004 at the Tokyo Takenotsuka Battle Sphere, Mammoth would return after his injured knee, but would face off against a much smaller Mineo Fujita as his opponent. Mammoth would work on the youngster by delivering stiff kicks to the face, before finally finishing off Fujita with the 29 Years Old to gain four points in the tournament. Mammoth found himself on the lucky end of facing an easier opponent despite his injured knee, but the next day would bring no such luck as Mammoth would face off against Mr. Gannosuke who had scored his first victory in the tournament on the show.

December 19, 2004 at the Tokyo Takenotsuka Battle Sphere, the match between Mr. Gannosuke and Mammoth Sasaki would end up being made into a Street Fight to allow Mammoth an easier chance to work a match instead of delivering moves on his bad knee. Mammoth would jump Gannosuke to start the match with a chair, and right away send the match outside the ring. Mammoth would then grab a garbage can and place it over Gannosuke and give and slam his chair into the garbage can placed over Gannosuke. Gannosuke would in turn make a come back and place a stack of chairs outside the ring and deliver a German Supplex outside the ring right on the stack of chairs. Gannosuke would then grab Mammoth and slam his him head first into the wall, and then the two would begin to brawl outside the arena into the streets. Mammoth would bodyslam Gannosuke in the street. The brawl would continue on top story of a building where Gannosuke would attempt to throw Mammoth off. Eventually both wrestlers would get back in the ring, in which Mammoth would introduce a barbwire board into the match. Gannosuke seeing the board would go for the clothesline right away to gain control of the match, and would deliver a Praying Powerbomb to Mammoth through the barbwire board. Mammoth would come back despite barbwire sticking into him by placing a chair over Gannosuke and delivering the Mammoth Home Run to Gannosuke. Gannosuke would barely be phased by it and deliver a clothesline to Mammoth. When Mammoth would return the clothesline, Gannosuke would grab Mammoth's arm and roll him into the Gannosuke Clutch and be pinned for his first pinfall defeat in the tournament, which would cause a 6 way tie for first place as well as causing Gannosuke to move right up with Mammoth in the standings. 

January 22, 2005 at the Tokyo Takenotsuka Battle Sphere, in the first match of 2005 for Mammoth, it would end in a better result then his final match of 2004. Mammoth would score a tournament victory over Onryo with the 29 Years Old, and put him in a good position in the tournament. 

January 23, 2005 at the Tokyo Takenotsuka Battle Sphere, that good position in the tournament would be ruined by the man that Mammoth made his wrestling debut against in GOEMON. Although Mammoth had owned GOEMON since June 8, 2001, it was GOEMON who would manage to escape both the Mammoth Home Run after having the chair placed over his head, when Mammoth would go for the Mammoth Home Run swing, GOEMON would throw the chair up in the air and move out of the way from the shot just in time. Mammoth would go after GOEMON, but again GOEMON would move out of the way and Mammoth would hit the top rope with the chair, causing the chair to bounce back and smack Mammoth in the head and GOEMON would roll up Mammoth with a school boy for the victory. Even worst for Mammoth, Gannosuke's hot streak would continue on the show with four straight victories placing him in first place all alone.

February 19, 2005 at the Tokyo Takenotsuka Battle Sphere, Mammoth would face off against Seiji Ikeda in the main event, in a must needed win. Mammoth would have to win to be able to tie Mr. Gannosuke, Garuda, and Soldier and stay alive in the tournament. Seiji Ikeda would be fighting for a automatic spot in the finals with a win, and would even control much of the match. Mammoth and Ikeda would brawl through out the crowd, and when Mammoth would set up the ladder and begin to climb it, Ikeda would get up and push the ladder and send Mammoth flying into the wall. Ikeda would the grab a chair and place it over Mammoth's head and deliver a Mammoth Home Run to Mammoth. Ikeda would bring back Mammoth in the ring, who would eventually come back to life and deliver a kick to head of Ikeda before putting a chair over Ikeda's head and delivering the Mammoth Home Run himself. Mammoth would not be able to put Ikeda away though, and Ikeda would come back with a Gannosuke Clutch on Mammoth. Mammoth would manage to kick out and would finally end up being too much for Ikeda and put  Ikeda away with the 29 Years Old for the victory and to tie for first place in the tournament. As a result of the four ties, two playoff matches would be assigned with the winners meeting each other in the finals of the tournament.

February 20, 2005 at the Tokyo Takenotsuka Battle Sphere, Mammoth would be put in a match against Mr. Gannosuke for the right to make it to the finals of the tournament. Mammoth and Gannosuke would start up where they left off last December, brawling all around the crowd. But this time instead of going outside the building, Gannosuke would use the props around ringside for his advantage. Which would include setting up a table right next to the ring and placing a ladder against the ropes. Gannosuke then picked up Mammoth and delivered a Fire Thunder on the table head first into the ladder injuring Mammoth's neck. Mammoth would be able to still continue, and when getting a hold of a chair, Mammoth would swing so hard at Gannosuke's head, it would literally knock out Gannosuke. Mammoth would then finish off Gannosuke with the 29 Years Old for the victory and to advance to the finals to meet Soldier. Gannosuke would be sent to the hospital after the shot given to him by Mammoth. 

Mammoth would still feel the pain in his neck from the Fire Thunder on the ladder, and Soldier would make sure to take advantage of that in the match. Soldier would attack Mammoth right at the beginning of the match, bloodying Mammoth up, but then Mammoth would make the mistake of bringing the ladder in the match once again as a weapon as he would place it over his head and begin swinging it around at Soldier. That move would end up costing Mammoth the tournament, as Soldier would take advantage of the ladder over Mammoth's injured neck and grab a chair and begin smashing the ladder into Mammoth's neck repeatedly until Mammoth was almost out of it. Soldier would then make sure to finish off Mammoth with a neck breaker to score the victory over Mammoth and win the WMF Round Robin Tournament. As a result, Soldier will now be bringing in his IWC friends to invade WMF as his wish from winning the tournament.

March 12, 2005 at the Chiba Blue Field, Mammoth would shock the fans at the Kintaro Kanemura Festival show, a now rival to WMF after running in to make the save for Kintaro Kanemura. Kanemura had been attacked after beating Hido and Jun Kasai and as the two were about to powerbomb Kanemura into fire, Mammoth quickly ran to the ring and cleaned house. Mammoth announced that he would remain with WMF, but would begin working with Kanemura's Apache Army promotion as well due to WMF's inability to pay Mammoth on a regular basis. 

Mammoth would deciding to work with the Apache Army also resulted in a fall out with Mr. Gannosuke. Mammoth was not only getting paid little, but felt the direction of WMF had lost its focus as the booker Gannosuke was focusing the promotion around himself instead of the younger wrestlers which was the main point of the promotion from the start. 

March 28, 2005 at Korakuen Hall, with Mammoth also agreeing to work with Kanemura also allowed Mammoth to get booked with other promotions like Big Japan as Mammoth would make his debut for the promotion by teaming with Daikokubo Benkei and defeating the team of Tetsuhiro Kuroda and Yuichi Taniguchi after Benkei pinned Taniguchi. 

April 1, 2005 at the Tokyo Shin-Kiba 1st Ring, Mammoth would still appear on WMF shows, but would no longer be booked as the focus of the promotion as much as he had been before. Mammoth would work an undercard gauntlet match on defeating undercard wrestlers like Lingerie Muto who would go on to become a popular wrestler in Munenori Sawa as well as isami who would go on to become Isami Kodaka in just minutes. 

April 3, 2005 in Saitama, Mammoth would then defeat Junji Tanaka in another undercard match who Mammoth had first faced off in a tag match dating back to July 10, 1998 as well as junji.com would team up with Mammoth back in March 2001 in FMW. Garuda afterwards would announce he would be quitting WMF due to a lack of pay and would find work in Michinoku Pro which offered less pay per show, but more shows overall than WMF. This would cause Gannosuke to become furious at WMF, but Mammoth who still held a high ranking in WMF was much more friendly towards Garuda about leaving. 

April 17, 2005 at the Tokyo Differ Ariake, Mammoth would then show how much more interested he was being with Kanemura then Gannosuke when he would be booked in a Apache Army tag team match for the WE LOVE SABU shows. Both Gannosuke and Kanemura would help book the shows, as Mammoth siding with Kanemura on the show would pretty much show where his heart was. Mammoth would team with Kintaro Kanemura and Tetsuhiro Kuroda against Masato Tanaka, Ikuto Hidaka and Minoru Fujita in the main event of the second show. Mammoth would mostly go after the smaller Hidaka and Fujita in the match, being able to deliver his power moves such as the chokeslam and the Mammoth Driver, but it would be in a losing effort as Masato Tanaka would end up knocking out and pinning Kanemura for the win. After the match, the locker room would get together and drink beers in the ring in tribute for Sabu in raising money for him to pay for his hospital bills. 

May 5, 2005 at the Sapporo Teisen Hall, Mammoth would work for Big Japan for their May tour in Northern Japan. Mammoth would then face cult favorite Necro Butcher. It would be the first time that a show had not been booked on May 5th by a former FMW wrestler since 1992. Mammoth and Necro would end up brawling all over the arena, including going upstairs before finding their way back in the ring with Mammoth finishing Butcher with the Mammoth Home Run for the win.

May 14, 2005 at the Tokyo Takenotsuka Battle Sphere, Mammoth would team up with Seiji Ikeda to face Soldier and Mad Man Pondo. Mad Man Pondo would be one of the wrestlers allowed to come in do to Soldier winning the WMF Round Robin Tournament. The match would be a falls count anywhere and would go all over the building as a result which end in Mammoth getting his revenge on Soldier and putting him away for the victory. The win would build Mammoth and Ikeda going in for the next day. Mammoth and Seiji Ikeda would team up to face the team of Mr. Gannosuke and Kensuke Sasaki on May 15, 2005 at the Osaka Delfin Arena. Gannosuke and Kensuke Sasaki would trade hard chops with Mammoth and Ikeda leaving Ikeda with his chest beat red for the rest of the day. Gannosuke would end up getting the pinfall victory over Ikeda with the Gannosuke Clutch for the win.

May 28, 2005 in Odaiba, Mammoth and Seiji Ikeda would finally get a tag team victory over Gannosuke with his partner this time being Mineo Fujita for the China-Japan Wrestling show with Mammoth getting the pinfall victory over Fujita. Mammoth would then challenge Gannosuke afterwards to a barbed wire death match in which Gannosuke would accept for the next WMF show on July 31, 2005.

June 8, 2005 at the Yokohama Bunka Gym, Mammoth would be returning to the building of several of his high profile matches in FMW for the first time since November 23, 2001. Mammoth would team up with Tetsuhiro Kuroda to face the team of Shadow WX and Yuichi Taniguchi for Big Japan . Mammoth would end up getting the victory over Taniguchi with the 29 Years Old for the victory for the old Team Zero, Team FMW, and Team Kuroda friends. Mammoth would team up with Kintaro Kanemura for the Apache Army show on June 10, 2005 at the Zepp Tokyo against K-Dojo's TAKA Michinoku and YOSHIYA with Kanemura getting the pinfall victory over YOSHIYA in a Hardcore Rules Match. 

Mammoth would then go on tour with Riki Choshu's Riki Pro due to his alliance with Kanemura. It would be his third tour for Riki Choshu promoted tours as he had toured with World Japan back in 2003 and 2004 as well. Mammoth would be pushed much better throughout the tour this time, getting victories over Jun Kasai and GENTARO before losing to Shiro Koshinaka on July 3, 2005 at the Wakayama Prefectural Gym. Mammoth would then team up with Big Japan's Ryuji Ito defeating the team of Takashi Sasaki and GENTARO when Mammoth pinned GENTARO with the 29 Years Old on the last show on the tour on July 4, 2005 at the Osaka Prefectural Gym # 2.

Mammoth would return to Big Japan and get a big victory over Abdullah Kobayashi on July 9, 2005 in a battle of the big men Hardcore Rules match after Mammoth would put away Kobayashi with the 29 Years Old. Mammoth's success wouldn't make much of an impact as he would be stuck in the opener with Hyoma on July 22, 2005 at Korakuen Hall losing to Daikokubo Benkei and Asian Cougar when Benkei would hit Hyoma with a Running Splash for the win. 

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