During an investigation of a serial killer in Tokyo, police are led to a hotel that may be where the next murder will take place. Detective Nitta Kosuke goes undercover and begins working at the front desk of the hotel. Yamagishi Naomi works at the front desk of the hotel. She is selected to train Kosuke for his front desk job. Kosuke is focused on catching the killer, but Naomi prioritizes the safety of the guests.