Kanzaki Ryuichi is a career detective assigned to Ikebukuro Police Department's criminal investigation division. On his first day of work, his partner, the senior detective Kuroki Kenji, is absent without notice. Kanzaki is tasked with hunting down his partner and begins looking into the places Kuroki may have gone. He finds Kuroki's police notebook near blood and suddenly gets a call with Kuroki saying he was involved in a kidnapping case.