Serious-minded Ai secretly feels sexually unfulfilled by her husband and his unusual tastes. Then his playboy brother Bunta suddenly visits their home, sees through her buried desire, and smoothly seduces her. Swept along by his words, Ai agrees to sleep with him “just once.” She rejects his persistent advances afterward, but her body cannot forget the full-body pleasure and the intense stimulation of his cock grinding against her vaginal walls—sensations her husband has never given her.