Mizuki, a junior, comes to stay at the home of the cohabiting couple Yoko and Kenta after her shower breaks down. From what Yoko mentioned, Kenta is supposedly an S-type, but to Mizuki, he clearly appears to be an M. As expected, she quickly discovers Kenta's submissive nature. With her around, Kenta finds himself gradually marked and dominated through slobbery, saliva-drenched kissing and aggressive sexual acts.