Itsuki runs a boarding house in Tokyo with two tenants. One is Saburo, and the other is Toshio, a dimwitted engineering student from the same university, nicknamed "Ichiban." Saburo is extremely satisfied with the boarding house, primarily because Itsuki's bedroom is right next to his, allowing him to secretly watch her masturbating from inside his closet. There's also a rumor circulating among tenants that anyone moving out will be called into Itsuki's bedroom for a farewell gift—she gives them a sexual send-off.