Nitta Kousuke, a police inspector in the Tokyo Metropolitan Police Force, is on the trail of a serial killer who leaves clues to the location of his next crime on his victims. Nitta uses the clues to discover that the Hotel Cortesia will be the site of the next killing, and goes undercover as a front desk clerk to help him unmask the killer. Yamagishi Naomi is the front desk clerk in charge of training him, and the two butt heads at every instance. Will they be able to unmask the killer before he strikes again?