Ventriloquist Tengan's wife Kazuko is bludgeoned to death with a trophy. Afflicted by multiple personality disorder, Tengan confesses that he may have killed her while he was unaware, but based on the circumstances, Tengan's apprentice Togawa, who was having an affair with Kazuko, rises as a suspect. Conan feels as though something is wrong with the case and investigates Tengan's home with Detective Takagi. He examines the sideboard where the trophies are displayed and realizes what has been bothering him. Later, Conan asks Takagi some questions and closes in on the truth behind the case..

As incidents thought to be the work of a demon known as the kamaitachi occur one after another, Bonzo is murdered in the annex of the inn. Conan notices something odd about the crime scene, and based on the crime scene Heiiji believes the culprit came to the annex through the outdoor bath. After hearing everyone's testimony, Conan and Heiji close in on the truth behind the case and realize who the culprit is from a casual remark...