The Oshima family lives with their daughter and her husband. - Her son-in-law, Kazuya, changes jobs and becomes a cleaner, and he is the only one whose living hours are different. - Kazuya's mother-in-law, Yuka, supports him with her embracing kindness. - Even though Kazuya knows that she is his wife's mother, he gradually becomes attracted to her. - At that time, they found out that they were not having sex with each other, and Kazuya couldn't stand it anymore and pushed Yuka down. - Even though she knows it's her step-son, her pleasure-hungry body regains moisture and swallows the cock deep into her vagina...