"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. Its members have a wide range of unique personalities, like the "Armored Detective" clad in armor, the "Literary Detective" with an excellent memory and love for books, "Netherworld Detective” who specializes in the occult, and many more. 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. 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... A detective simulation adventure game in which 14 detectives confront a serial killer. During the game, investigation parts in which the detectives investigate will occur. However, the player’s avatar, the Incompetent Detective, does not have a special skill. So the key is for the player to give detailed instructions to their reliable detective colleagues and have them carry out the investigation on your behalf.