Yoshio Kobayashi the 7th is a descendant of the original Yoshio Kobayashi from Edogawa Ranpo's novels, serving as a boy detective in Tokyo during the year 2117. He is a member of the Boy Detectives Club, an organization dedicated to protecting the city's peaceful life from unknown threats, particularly those originating from hidden and mysterious criminal organizations. His primary motivation is to aid in these protective efforts, though situations often unfold in unexpected ways.

He operates within a long-standing conflict between the detective lineage of Kogoro Akechi and the criminal lineage of the Fiend with Twenty Faces, a battle that has persisted for seven generations. As the seventh-generation boy detective, he represents the latest in this enduring legacy.