A chaste married woman falls into the temptation of a lustful sportsman's big dick. Ibuki, a married woman who starts going to a personal swimming school to improve herself even though she is no longer having sex with her husband... Ibuki, who can't get the big dick of the instructor Tanaka she met there, has a physical relationship with Tanaka. She becomes addicted to the muddy adulterous sex with Tanaka that she cannot experience with her husband. A married woman who can't be held by her husband finds out the joy of being a woman with her instructor's big cock...