The school is about to hold a school parade, but the headmaster keeps receiving threatening letters from the “after-school magicians” who threaten to stop the demolition of the old school building immediately. Since the threatening letters are related to the Seven Unthinkable Legends surrounding the old school building, the school’s Reasoning Research Club plans to investigate these legends in order to find the truth. However, during the investigation, members of the club are killed by the “after-school magicians” one after another, and even Miyuki Nanase is unfortunately attacked. With the help of Detective Isamu Kenji, Kaneda discovers that the legend is related to an inside story about the Takahata Pharmaceutical Company that happened 30 years ago, and that the killer’s motive is related to the case of a female student who disappeared ten years ago while investigating the legend.