“Yatsuzakikou” is a serial killer who has killed more than 100 people and thrown the country into chaos. To put an end to his murder spree, the finest members of the “Detective Alliance,” an organization made up of only the top detectives, launch a joint investigation. Around the same time, an ordinary boys’ high school student named Wato Houjou, who longs to become a detective, arrives at a remote island where the Detective Alliance is headquartered under the guidance of a mysterious man named “The Sage Detective.” On the island, Wato could not hide his excitement at meeting the Detective Alliance he so admired. However, when the detectives suspected him to be Yatsuzakikou, he was at a loss for words. Yatsuzakikou had already infiltrated the island, and many detectives have been murdered. To clear his name, Wato and the Detective Alliance leader, the “Ideal Detective,” launch an investigation. 14 detectives remain alive. And Yatsuzakikou is among them.