One day, Amakusa Natsuki—the hope of the Tokyo Metropolitan Police Department—meets an unusual high schooler named Shiki Yuuya. Natsuki's interest in the high schooler is piqued after Yuuya happens to be passing through the scene of a difficult murder case and determines the perpetrator with ease. How did he know who the killer was? When an incident later takes place at Yuuya's high school, the two happen across each other again...