Minoru Tatsukawa is a member of the Kuroda Clan, a yakuza organization, and serves as one of Kumiko Yamaguchi's most loyal followers. He entered the clan at the age of fourteen after Kumiko took him in when he had nowhere else to go, calling him a younger brother because the family did not accept underage members. Alongside his close associate Tetsu Asakura, Minoru is deeply devoted to protecting and watching over Kumiko, often to the point of overenthusiasm that risks exposing her secret identity as a teacher. The two can frequently be seen running a takoyaki stand near Kumiko's school, using the business as a cover to remain close and ready to help if needed. Minoru takes his duty seriously and will go to extreme lengths to ensure Kumiko's well-being, whether she is threatened, mocked, or otherwise harmed. Despite his intense protectiveness, his core motivation is simply to assist the person who gave him a second chance. He has a sibling-like bond with Kumiko, precluding any romantic feelings, and works alongside Tetsu as a constant support. Within the story, Minoru functions as a background ally who provides comedic relief through his earnest but clumsy attempts to help, while also demonstrating the unbreakable loyalty that defines the Kuroda Clan. His abilities are not highlighted in great detail, but as a yakuza member he is capable in physical confrontations and operates with the discipline expected of the organization. His character remains consistent throughout the series, showing little personal growth beyond his unwavering dedication.