Yamane Tasuku, a member of the Scientific Experiments Club, is troubled by three things: Ohtomo picks on him, he's always left behind in conversations, and most troubling of all is that he doesn't know how to become a member of the Boy Detectives' Club.

To escape the enemies targeting Fukiya, the death row prisoner they're guarding, the Boy Detectives' Club takes refuge in the abandoned building that Kobayashi had once been using as his base.