Two years ago, Yuna married her current husband, who has recently become very busy, leaving Yuna alone at home often with her stepson, Ataru. To satisfy her sexual desires, Yuna began masturbating every day in the bath. One day, Ataru accidentally sees Yuna alone in the bathroom. Unable to restrain himself, he quietly reaches out to touch Yuna's sleeping body. In that moment, a new, forbidden emotion begins to stir between them.