An unassuming worker in a long-established public bathhouse is really the lustful 450-year-old vampire Ranmaru Mori! The heir to this esteemed Koi No Yu Bathhouse, Rihito Tatsuno, is a fifteen-year-old virgin—who is about to fall in love for the first time with a girl in his class! Ranmaru begins to weave a desperate plan to prevent Rihito from losing his virginity and to make him fall for Ranmaru instead, so the bloodsucker can eventually have pure, eighteen-year-old virgin blood for his own vampiric self!