It is the 2030s. The Boy Detectives Club gathers under the enigmatic detective Kogorō Akechi. The group solves cases big and small using their unique skills. One day, a club member, Kensuke Hanazaki, meets a boy named Yoshio Kobayashi. Kobayashi's body cannot die due to the effects of the 'Unidentifiable Mist,' but he longs for death and avoids contact with others. Intrigued by him, Hanazaki invites him to join the Boy Detectives Club. Their meeting is linked to the fate connecting Kogorō Akechi and the era's greatest villain, the Fiend With Twenty Faces.
