Shoko lives with her husband, daughter, and son-in-law. Although she leads a peaceful life, she is unsatisfied due to her sexless marriage. One day, she accidentally witnesses her son-in-law, Toshio, masturbating... The enormous cock that appeared in the darkness captivates Shoko's heart. Unable to hold back, she constantly tempts him, regardless of the place. Toshio, who has been frustrated by his wife's lack of affection, finally gives in to his mother-in-law's lewd behavior and starts looking forward to their acts...
