The boys' mothers went on a trip, so they came to stay at their cousin's house, Natsutsuki, who said she would take care of them and make them eat. Natsutsuki has always Kokoro about sex, and whenever she came to stay, the boys would always get seduced and jerk off, so they were worried about this time too, but sure enough, Natsutsuki started rubbing her big tits against them and seducing them again...