Tatsuya, who lost his mother, has been unable to get along with Saeko, who became his father's second wife for a year. Tatsuya's father has also gone abroad, and Tatsuya unintentionally behaves unfriendly towards Saeko. Saeko behaves stubbornly without worrying about such things, but... One day, Tatsuya accidentally peeps at Saeko's masturbation. Tatsuya couldn't hide his surprise. It was because Saeko's finger was stuck in her anus. Tatsuya, who can't get away from his usually chaste mother's vulgar anus with his back open...
