Aki Hayakawa was a young man with medium-length black hair and sapphire blue eyes. He usually wore his hair in a topknot style. He often wore the Public Safety Devil Hunter suit and tie. He also donned earrings and usually carried his sword on his back.

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, hated to see people get hurt.