Nanami, a mother who has raised her only daughter alone since her husband passed away. Her daughter has grown up to be a fine young woman, and now she's married and living with her. One day, while living an ordinary but happy life, she happens to peek at her daughter and her husband's nighttime activities and is shocked. Her adopted son-in-law, who is a gentle and serious man, is making her daughter cum over and over again with his wild, intense hip thrusts. Seeing this brings back memories of her past as a sex addict and creampie slut, and she can no longer control her sexual desire...