In order to save up for a home, mother An enjoys spending quality time with her daughter and son-in-law who have come to live with her. However, her husband, who is much older than her, has lost his libido, and she has to satisfy herself, leading to lonely days. One day, An is Kokoro by her son-in-law Koichi's rare large cock as he secretly peeks at her masturbating. She tells herself that it is for the sake of a good relationship between her and her husband, and begins to violently seduce him around the clock. Unable to resist his mother-in-law's lewd behavior, Koichi is brought to orgasm countless times, and can no longer live without her...