Aki generally appears to be a very stoic person. He acts mature and sometimes blunt to the point of rudeness when he is with his fellow Devil Hunters, but he is actually fairly softhearted. He has a tendency to get attached to others easily, and hates to see people get hurt, especially his close friends. His family was killed by the Gun Devil, leaving him as the only survivor. He now hunts devils and seeks revenge on the Gun Devil. Aki smokes cigarettes quite a lot.