Tetsuo is a biker and the only adult member of Mitsui’s gang, which included Norio Hotta and his cronies, in addition to some other delinquent high school students. It would appear that he is the gang leader, although he largely defers to Mitsui when they launch their attack on the Shohoku basketball team. He appears to be in his late 20's/30s, and is the gang’s most experienced and capable fighter. Tetsuo succeeds in knocking out five Shohoku players, among them Rukawa and Miyagi, but is beaten brutally by Sakuragi.

After Mitsui leaves the gang and rejoins the team, Tetsuo later runs into him after the former is heading home after getting his knee checked. He accepts Mitsui as an athlete, reaffirming the latter’s decision to rejoin the team. Tetsuo makes an additional appearance in the anime when on the morning of Shohoku’s match with Shoyo, he is chased and cornered by the non-Shohoku members of his gang, who beat him up in a bid to challenge his leadership. Mitsui comes upon them, but refuses to fight because of the promise he made to Coach Anzai not to fight again. Tetsuo stands up for him, but gets knocked out. However the timely intervention of Sakuragi and his Gang enables the two basketball players to leave the scene, resulting in Tetsuo teaming up with Sakuragi’s Gang to take out Ryu and his cronies.