Receiving news that the younger cousin who just took the university entrance exam is coming from the countryside to visit, Shirakawa is very happy because finally she gets to meet her childhood cousin after a long time without contact. She is very attentive and enthusiastic when he is here, doing everything to make her cousin feel most satisfied, even bathing together - one of the unforgettable memories of their childhood. But time has passed, now he has become a teenager, at an age of intense psychological development, so just one sensitive factor like the recent shared bath will make him lose his rationality. Adding to that, the promiscuous cousin always exposes herself naked and performs inviting gestures very seductively, unwanted things are sure to happen.