He got his start loading trucks for New Japan Pro-Wrestling (NJPW), and after some months of persuasion finally convinced head trainer Animal Hamaguchi to accept him into the dojo.

Three days later it was revealed that Kojima would return to New Japan to compete in the 2006 G1 Climax, where he would go to lose in the finals against former tag team partner and rival Hiroyoshi Tenzan.

In July 2007, Kojima shocked the All-Japan Army when he betrayed them and joined the Voodoo Murders, where he was quickly made the group's co-leader along with TARU.

[22] Meanwhile, the newly renamed Kojima-gun expanded to include Taka Michinoku and Nosawa Rongai, who in turn used his connections to get MVP to also join the group.

[35] After picking up three wins and one loss in their first four matches, Kojima and Makabe were defeated by the Billion Powers (Hirooki Goto and Hiroshi Tanahashi) on November 4, causing them to narrowly miss advancing to the semi-finals of the tournament.

[37] Tencozy wrestled their return match as a tag team on December 4, defeating CHAOS members Hideo Saito and Takashi Iizuka.

[38] On January 4, 2012, at Wrestle Kingdom VI in Tokyo Dome, Kojima and Tenzan defeated Bad Intentions (Giant Bernard and Karl Anderson) to win the IWGP Tag Team Championship for the third time.

[40] On July 22, Kojima and Tenzan defeated Iizuka and Yano in a decision match to regain the newly vacated title.

[45] On December 9, Kojima made a rare appearance for Pro Wrestling Noah, unsuccessfully challenging Takeshi Morishima for the GHC Heavyweight Championship.

[46] On April 7, 2013, Kojima unsuccessfully challenged visiting Rob Conway for the NWA World Heavyweight Championship at New Japan's Invasion Attack event.

in a four-way match, which also included Takashi Iizuka and Toru Yano, and Manabu Nakanishi and Strong Man, starting Kojima's sixth reign as champion.

[50] However, a victory over reigning IWGP Heavyweight Champion Kazuchika Okada on the final day of the tournament earned Kojima a shot at the title.

[52] Kojima returned to the ring on November 9 at Power Struggle, where he and Tenzan lost the IWGP Tag Team Championship back to K.E.S.

[56][57] The following day, Tencozy unsuccessfully challenged The IronGodz for the NWA World Tag Team Championship with Conway pinning Kojima following a low blow.

[58] On February 9 at The New Beginning in Hiroshima, Kojima made his first successful defense of the NWA World Heavyweight Championship against Big Daddy Yum-Yum.

[59] Two days later at The New Beginning in Osaka, Tencozy defeated Yum-Yum and Michael Tarver to earn another shot at the NWA World Tag Team Championship.

[61] Six days later, during New Japan's trip to Taiwan, Kojima made his second successful defense of the NWA World Heavyweight Championship against Rob Conway.

[64] On May 25 at Back to the Yokohama Arena, Tencozy successfully defended the NWA World Tag Team Championship against Brisco and Conway and K.E.S.

After successful defenses against Jeremiah Plunkett, Damien Wayne and Houston Carson, Kojima lost the title back to Rob Conway on June 2 in Las Vegas.

[69] The following month, Tencozy took part in the 2014 World Tag League,[70] where they finished with a record of four wins and three losses, failing to advance to the finals.

[71] In late 2014, Kojima began making appearances for Pro Wrestling Noah, which culminated in him unsuccessfully challenging Naomichi Marufuji for the GHC Heavyweight Championship on January 10, 2015.

[77] Afterwards, Kojima backed out of the 2016 G1 Climax and gave his spot to Hiroyoshi Tenzan to give his longtime tag team partner one final chance to win the tournament.

[80] That same day, Kojima and Ricochet, now teaming with David Finlay, defeated Adam Cole and The Young Bucks to regain the vacant title.

[81] They lost the title to Los Ingobernables de Japón (Bushi, Evil and Sanada) in a four-team gauntlet match at Wrestle Kingdom 11 in Tokyo Dome on January 4, 2017.

[82] On March 6, Tencozy defeated Tomohiro Ishii and Toru Yano to win the IWGP Tag Team Championship for the sixth time.

[88] On May 24, 2024 he returned to the CMLL as part of the CozyMAX (Okumura) tag team, they lost against Los Depredadores (Magia Blanca & Rugido).

[91] On the following week's Impact!, Kojima made his debut confronting Violent by Design where he challenged VBD member Joe Doering to a match at Against All Odds.

Together, they defeated World Titan Federation (Tom Lawlor, Davey Boy Smith Jr., Richard Holliday, and Josh Bishop) in a War Chamber match.

Together, they defeated The Second Gear Crew (Matthew Justice and 1 Called Manders) to win the vacant MLW World Tag Team Championship.

[101] Kojima, along with fellow NJPW wrestlers Hiroshi Tanahashi, Hiroyoshi Tenzan, Kazuchika Okada, Tetsuya Naito and Toru Yano, appears as a member of the gang Justis in the 2016 video game Yakuza 6: The Song of Life.