A faithful wife falls for the seduction of a lustful sportsman's huge cock. Ibuki, a married woman who has become sexless with her husband, starts attending a personal swimming school to improve herself... She meets an instructor there, Tanaka, and cannot get his huge cock out of her head. She ends up having a physical relationship with Tanaka and becomes addicted to the messy extramarital sex that she cannot experience with her husband. The sexless wife, who cannot be held by her husband, learns the joys of being a woman through the instructor's huge cock...