Ultimate Fighting Championship

Fujii made his debut in Ultimate Fighting Championship during the UFC 23 tournament in Japan, where he first faced the newcomer Masutatsu Yano. The bout started slow, with Fujii defending with strikes and submissions attempts against his opponent's wrestling acumen, but in the second round, Fujii stunned Yano with punches and scored the knockout victory.^[2]

He advanced to the next round and found himself against fellow shoot-style practitioner Kenichi Yamamoto, a former apprentice of both Nobuhiko Takada and Akira Maeda. The heavier Fujii controlled the takedowns and applied ground and pound through the guard, threatening with a leglock attempt at the end of the round. At the second, Yamamoto pulled guard and Fujii repeated his strategy, but this time Yamamoto caught Fujii with a kneebar from the bottom, making him tap out.

PRIDE Fighting Championships

After joining Naoya Ogawa's team in Universal Fighting-Arts Organization, Fujii got to debut in PRIDE Fighting Championships in May 2004. His first bout was against Korean newcomer Jin O Kim, whom Fujii dominated with knees and punches before submitting him to a rear naked choke.

Fujii then was pitted against the returning Igor Vovchanchyn, former runner-up to the PRIDE Openweight Grand Prix 2000. Immediately overpowered by Vovchanchyn, the Japanese tried to avoid his striking, which gained him a red card. Minutes later, Vovchanchyn dropped Fujii and finished him with soccer kicks.

Pro Wrestling Zero-One (2003–2004)

He was introduced in Zero-One in January 2003 as a new ally to his mentor Ogawa.^[3] Immediately after, Fujii and him challenged the reigning NWA Intercontinental Tag Team Champions, Matt Ghaffari and Tom Howard, but were defeated. Fujii remained as a Japanese loyalist, teaming up with native wrestlers against Ghaffari and his American faction from UPW, while also doing small appearances for shoot-style wrestling promotion U-style, founded by Kiyoshi Tamura.

Ogawa and him teamed up again in July, when they competed at the OH Tag Festival. They were successful, reaching the finals after eliminating Howard' and Ghaffari's own teams, as well as Mexican legends Dos Caras Jr. and Lizmark Jr., and then defeated Kevin Randleman and The Predator at the finals to win the tournament. Fujii also followed this victory by winning also the U-style tournament Kiyoshi Tamura Challenger, earning him a match against Tamura which Katsuhisa lost. Ogawa and him kept teaming until the end of the year, when they both left Zero-One for Hustle.

Hustle (2004–2006)

Fujii wrestled in Hustle as a member of Ogawa's Hustle Army. Being given the nickname of "Shamoji" ("Gamecock") by Ogawa, Fujii was portrayed here as an optimistic underdog who always tried his best despite constantly failing. It was better exemplified by his finishing move, a diving elbow drop ironically baptized as AHE or Atareba Hyappatsuhyakuchu Elbow (translated as "100% Hitting Chance Elbow"), which he constantly boasted of, yet never managed to land on his opponent due to the long range he chose to execute it.^[3] He battled repeatedly the forces of Generalissimo Takada's Monster Army over the years, getting occasional wins in tag team matches, until leaving Hustle in March 2006.