The Iori family, parents and children, were enjoying a happy trip to a hot spring surrounded by nature. However, the mother Ryoko's body is so attractive that it makes her son Masahiko have evil thoughts. Although she loves her husband, Ryoko gives in to her son's desires... Mother and son gradually get sucked in, and they make love as if devouring each other's bodies. And finally, the son stands before his father to take his mother away...