Sachi Takamaki is a intern news reporter for a newspaper publishing company. She met Kurama Hirose, a private detective who was nicknamed the "Poker Faced Detective" because he never shown any emotion except a serious face. In curiosity, Sachi asked why he's always emotionless. Kurama's reply is that he must maintain a his heartbeat not less than 60 and not exceeding 100 beats per minute or he'll die.