A mysterious informant has appeared, catching serial killers that the police don't even know about. Among the police who rush to the scene after receiving the call is Shiro Isogai, a police sergeant from the Public Safety Division, which is supposed to be outside his jurisdiction. He is trying to get to the bottom of the identity of the mysterious informant in order to catch the serial killer who murdered his fiancée. And he finds out... a young girl in her 20s, Hinata Kuroi.