Miru is Yuzuru's sister-in-law, the three of them have been living together for two years. Recently, because Miru's husband couldn't find a job, he often drinks and sleeps in the living room. In those moments, Yuzuru secretly enters the room to watch Miru, asking if she has fallen asleep. At first, Miru felt scared, but since Yuzuru didn't do anything else, she felt relieved and pretended to be asleep. After many efforts, Miru's husband finally found a job, but the job requires working night shifts, so Miru may not be able to be intimate with her husband anymore. On that day, Yuzuru sneaked into Miru's room as usual, but this time he couldn't control himself and had sex with Miru! Although they knew it was wrong, because they had not been sexually satisfied recently, Miru's body responded to Yuzuru's every move, making her not want to stop! So Miru continued to pretend to be asleep, allowing her younger brother-in-law to cuckold her own husband, enjoying the pleasure of sexual intimacy together!