Tetsuji is a member of the anti-yakuza vigilante group known as The Reapers, whom Kazuma Kiryu faces off against during the Hitman sidestory in Yakuza 3.
Background[]
Tetsuji had, at one point, tried to leave his life as a yakuza behind. To that end, he'd joined the Honest Living Association and tried to find work as a civilian. However, he was fired from multiple jobs after his employers discovered he'd once been a yakuza and any time he told possible employers about his past beforehand, they refused to hire him because of it.
Eventually, having become frustrated with his mistreatment due to his past, he gave up on being a civilian and tried to return to his work as a hitman. Unfortunately, his former family refused to take him back because he tried to leave the life behind. Ultimately, he was approached by the Reapers, who offered him work as a hitman for their anti-yakuza cause.
Yakuza 3[]
While Kiryu is visiting the Honest Living Association's offices in Okinawa, he is told about Tetsuji's presence nearby and he decides to try to recruit him into the HLA.
When Kiryu confronts Tetsuji, the hitman recognizes him, since he'd been told about Kiryu's successful transition to civilian life back during his first attempt at going straight with the HLA. Tetsuji tells Kiryu about his failed attempt at turning a new leaf and insists that he cannot leave his profession behind, since he's convinced he'd just failed again.
The two men fight each other and Kiryu wins. Now doubtful about his combat skills and, with his hopes restored due to Kiryu's affirmations that leaving the life behind is possible in the right circumstances, Tetsuji decides to go to the HLA and try to become a civilian once more.