Yumi lives happily with her husband, daughter, and son-in-law Yuma, but her sexless marriage leaves her masturbating alone. Then she discovers that Yuma has been using her as jerk-off material. Feeling sorry that his oversized cock has kept him from having sex for so long, Yumi tells herself she is doing it “for the couple” and starts teasing him whenever she gets the chance. After being kept on edge by his mother-in-law’s shameless advances day and night, Yuma and his huge cock finally reach their limit...