Tōko Kisaragi is a detective in the Investigation 1 Section 11 of the Tokyo Metropolitan Police Department. Her senior, Detective Hideaki Takano, has decided to move to the Public Security Bureau. Hideaki Takano's transfer will be carried out in one week. During this time, a murder takes place. A wealthy man is found dead in his home. His throat has been cut and a blue flower placed within the wound. Also, the victim's wife, Mayumi, is missing. A newspaper then receives an email from Kurasuta 16, professing themselves as the murderer. The email also implies the location of Mayumi. Since Detective Hideaki Takano is soon to transfer to the Public Security Bureau, Tōko Kisaragi feels more pressure and responsibility to solve the crime..