Yamane Tasuku, a younger member of the Scientific Experiments Club alongside Ohtomo, is troubled by three things. The first is that Ohtomo picks on him too much. The second is that he's always left behind in conversations. The third and most troubling of all is that he doesn't know how to become a member of the Boy Detectives' Club. One day Yumeko approaches him, mistaking him for a member of the club and asking him to investigate a case in which the school's most attractive boys are becoming victims of theft. But Yamane is so pleased by the mistake that he accepts the job...