After dating and getting married, their married life became stale after five years, leading to a sexless relationship. Jun, her husband, was a simple and earnest man who was rejected by his wife in matters of intimacy. He couldn't bring himself to visit a hostess bar, and spent his days in frustration. One day, his wife went back to her hometown for a friend's wedding for three days. Worried about housework while his wife was away, Saki, his wife's older sister, came over with some home-cooked meals. "You're so young, yet you're already sexless... Well, I'm the same way," Saki, the unsatisfied married woman, teased the young Jun who was brimming with pent-up sexual desire. While his wife was away, the two of them indulged in each other's bodies... "Even though we're technically brother and sister-in-law, it's not cheating, right?" Jun climaxed multiple times from the mature body and intense pleasure he couldn't experience with his wife.

恋愛して結婚して…夫婦生活も5年も経つと関係もマンネリ化してセックスレスになってしまった。朴訥で真面目な夫の潤は妻に性の営みを拒絶され、風俗にも気後れして行けず悶々とした日々を送っていた。そんなある日、妻が友達の結婚式で3日間帰郷することになった。嫁さんが不在の間の家事を心配して、妻の姉の咲が総菜などを持ってやって来る。「若いのにあなたたちもうセックスレスなの…あらあら、ウチもそうだけどね…」欲求不満な人妻の義姉は性欲が溜まっている若い潤を誘惑する。そして嫁（妹）が不在の間、二人はカラダを貪り合って…。「義理だけど姉弟だから浮気じゃないんじゃない」妻とは味わえない熟れた肉体と震えるほどの快楽に潤は何度も射精するのであった。