Kaoru Kanou, a corporate president who is under suspicion for arrest, holds a ballroom event. Among the invitees are Shinjūrō Yūki, a curious detective, his strange assistant, Inga, and Rie, the daughter of police detective Rinkako Kaishō. During the event, Kanou is mysteriously murdered by a knife in his back, with suspicions placed on a member of the SP police who was found shot dead in the hallway. However, thanks to Shinjūrō's detective work, along with the strange abilities of Inga, who transforms into an adult capable a forcing an answer to any one question she asks someone, they soon discover the culprit is Kanou's wife, who wanted him to die a hero.