Aunt Toshiyo regularly looks after her late sister's family. While taking care of her, she ends up having an affair with her sister's husband, Naoya. When her nephew, Noboru, who secretly harbors a love for her, finds out, he feels intense regret and anger... Unable to suppress his urges towards Toshiyo, he forcibly penetrates her ass, saying, "If the front hole is my father's, then the back hole is mine!" Swept away by his strong feelings, Toshiyo is unable to talk to anyone about it, and continues to quietly feel the throbbing in her anus...