He is a Public Safety Devil Hunter working under Makima's special squad who has contracts with the Curse Devil and Future Devil, and a former contract with the Fox Devil. Aki is a young man with medium-length black hair that he usually wears in a topknot style (shoulder-length with long bangs when untied) and blue eyes. In the past when he and Himeno met through Kishibe and became partners, Aki used to have shorter hair.