At the Millennium Research Institute, a counseling center that handles unusual requests, Ichirou Umoregi, alias 'Akuma-kun,' leads the way. He's a brilliant young prodigy, appearing only once in a millennium, yet unaware of his true lineage. Teaming up with Mephisto III, his partner, Akuma-kun delves into the enigma of his heritage while tackling perplexing cases in this intriguing detective duo tale.