He is an assassin and is one of the strongest swordsmen of the Kiheitai, an extremist Joui faction bent on causing world destruction. He regularly keeps his headphones on, as well as sun glasses even while others are talking to him. Bansai is shown to have an extremely calm demeanor, which covers up the fact that he has a vicious, almost cruel personality which actively seeks out conflict. He carries and is skilled at playing a shamisen, which also doubles as a tool for tying others up or as a weapon similar to a garrote. On top of being famous as a skilled swordsman, Bansai is also a talented songwriter. He works as a music producer under the name "Tsunpo", and Otsu's newer songs are written by him.

Spoiler

During a major fight in the Silver Soul War, Bansai sacrificed his life in order to protect his fellow members of the Kiheitai.

Bansai's name is roughly based on that of a hitokiri of the Bakumatsu era, Kawakami Gensai, while his stage name is based on the musician Tsunku.