Aki Hayakawa was a young man with medium-length black hair that he usually wore in a topknot style (shoulder-length with long bangs when untied) and blue eyes. Aki generally appeared to be a very stoic person. He acted mature and sometimes blunt to the point of rudeness when he was with his fellow Devil Hunters, but he was actually fairly softhearted. He had a tendency to get attached to others easily, and hated to see people get hurt, especially his close friends.