The Oshima family lives with their daughter and son-in-law. Kazuya, the son-in-law, has changed jobs and become a cleaner, so his schedule is different... But his mother-in-law, Yuka, supports him with kindness. Even though he knows she is his wife's mother, Kazuya is gradually drawn to her. Then, they find out that they are both sexless, and Kazuya can't help but push Yuka down. Even though he knows she is his son-in-law, his body is starved for pleasure and regains its moisture, swallowing her cock deep into his vagina...