After losing their parents, the brother worked part-time to support the family, while the younger sister, Mikako, comforted him with pretend sex games. One day, while the brother was out, their uncle came to the house and assaulted Mikako. Yielding to his threats, she was creampie fucked, and afterward, she was trained like a toy and repeatedly used by her lust-crazed uncle. When the brother returned home, he discovered his sister climaxing over and over again through intense sex.