Mori Ranmaru works as a live-in part-timer at a long-established public bathhouse. His true identity is a 450-year-old vampire. Seeking the ultimate taste of "the blood of an 18-year-old virgin," he continues to protect the virginity of 15-year-old Rihito, the only son of the bathhouse owner. However, a crisis arises as Rihito reaches puberty—he falls in love at first sight with a girl in the same class! "Rihito's virginity must be protected at all costs!! Love shall not be allowed!!" Ranmaru's desperate "Operation Virginity Loss Prevention" begins!