Koumei is a hotheaded person who almost always ends up in confrontations when engaged in conversation. He prefers using his fists to solve issues rather than his head, and would rather pick a fight than strategize. At one point, Koumei was approached by Hisashi Amachi and asked to join the Amachi Army. However, Koumei initially refuses the offer. But when Amachi tells him that he can clear his father's debt if he decides to join his faction, his mind changes. Hisashi became a friend over time.