A decade ago, the 450-year-old vampire Ranmaru Mori was rescued from certain death by a naive young boy named Rihito Tatsuno. Following that, Ranmaru began working at the Tatsuno family's bathhouse, secretly planning to drink Rihito's virgin blood once he reached adulthood. However, this plan is jeopardized when Rihito develops feelings for a girl on his first day of high school. Worried that Rihito might lose his purity, the envious Ranmaru starts covertly watching over him, protecting him while keeping his vampire identity hidden.
