Tanaka debuted in Extreme Championship Wrestling (ECW) on March 1, 1998 at Living Dangerously, defeating Doug Furnas. In July 1998, he began a feud with Mike Awesome, who he defeated at Heat Wave 1998.
Tanaka formed a short-lived tag team with Balls Mahoney, and at November to Remember on November 1, 1998 they defeated The Dudley Boyz to win the ECW World Tag Team Championships. In doing so, he became the first person to ever kick out of the Dudleys' 3D finisher. The Dudley Boyz would regain the titles five days later.
Tanaka returned to ECW in the summer of 1999, this time vying for the ECW World Heavyweight Championship. On September 19 at Anarchy Rulz, Taz, about to leave ECW, defended the ECW World Heavyweight Championship against the returning Mike Awesome and Tanaka in a three-way dance. After just two minutes, Taz was eliminated by a combined assault at the hands of his opponents. After a further eleven minutes of brawling, Awesome pinned Tanaka with a Kamikaze Awesome Bomb to become the new ECW World Heavyweight Champion.
Tanaka faced Awesome for the title at November to Remember on November 7, but was defeated once more. He finally overcame Awesome on December 17, 1999 at an ECW on TNN television taping in Nashville, Tennessee, becoming the first ECW World Heavyweight Champion not to be an American citizen. After the match, Awesome shook Tanaka's hand and fastened the belt around his waist in a show of respect, then attacked him as he left the ring and powerbombed him through a table. Awesome would regain the title at the next week's television taping in White Plains, New York on December 23.
Continuing his rivalry with Awesome, Tanaka joined forces with Tommy Dreamer to face Raven and Awesome. Dreamer and Tanaka defeated the Impact Players for the ECW World Tag Team Championship on February 26, 2000 in Cincinnati, but lost them to Mike Awesome and Raven on March 4, 2000 at The ECW Arena. This led to a tag team three-way dance at Living Dangerously on March 12, with Tanaka and Dreamer facing ECW World Tag Team Champions Mike Awesome and Raven and the Impact Players. Tanaka pinned Awesome, who had already defended his ECW World Heavyweight Title earlier that night, beating Kid Kash, costing Awesome and Raven the tag team titles, but lost the match after Dreamer was pinned by the Impact Players.
Tanaka's feud with Awesome was brought to an abrupt end when Awesome left ECW in April 2000. He faced Balls Mahoney on an episode of ECW on TNN and at Hardcore Heaven 2000. He remained with ECW until mid-2000.
On June 12, 2005, Tanaka revived his feud with Mike Awesome at the World Wrestling Entertainment (WWE)-produced ECW One Night Stand 2005 reunion pay-per-view. He was defeated after Awesome delivered a running Awesome Bomb through a table outside the ring and followed up with an Awesome Splash. He returned to WWE one year later at ECW One Night Stand 2006, losing to Balls Mahoney.