Kana Kurosaki has been appointed to be in charge of investigating the serial killer X. However, there is little information about X, not only her name but also her background is unknown, and there is not even a proper photo of her face. Kana's father, Goro, who was once a special investigator, also worked hard to investigate X, but lost his life in the line of duty. Kana visits Eiji Kagami, a former subordinate of her father's and the man closest to X, to ask for his cooperation in her investigation. But she is