They fell in love and got married... After five years of married life, their relationship became stale and they became sexless. Jun, a simple and serious husband, was rejected by his wife for sex, and was too shy to go to a brothel, so he spent his days in agony. One day, his wife went back home for three days to attend a friend's wedding. Worried about the housework while his wife was away, his wife's older sister Saki came over with some prepared food. "You're young, but you're already sexless... Oh my, it's the same in my house..." The frustrated married woman's sister-in-law seduces the young Jun, who has pent up sexual desire. And while his wife (younger sister) is away, the two of them devour each other's bodies... "We're step-siblings, but it's not cheating." Jun ejaculates many times over the ripe body and the trembling pleasure he feels, which he can't experience with his wife.