The Tachibana family consists of husband, wife, Reika, and their son, Ataru. They are an ordinary family, living in an old Japanese house inherited from their parents, which they renovated in a fashionable way. One day, Reika, unable to bear the sight of Ataru's room being dirty, is cleaning it when she discovers a dirty book. As she flicks through the pages, thinking it's proof that Ataru is growing up healthy and reaching puberty, she realizes that the book is far too erotic. Before she knows it, Reika is groping her pussy and indulging in masturbation...