Miru is Yuzuru's sister-in-law, the three of them have been living together for two years. Lately, because Miru's husband couldn't find a job, he often drinks and sleeps in the living room. In those moments, Yuzuru sneaks into 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 also felt relieved and pretended to be asleep. After many efforts, Miru's husband finally found a job, but the job required him to work night shifts, so it seems like Miru will not be able to have sex with her husband anymore. On that day, Yuzuru still sneaked into Miru's room as usual, but this time he couldn't control himself and had sex with Miru! Even though they knew this was wrong, because they had not been sexually satisfied recently, Miru's body responded to each thrust of Yuzuru, making her not want to stop! So Miru continued to pretend to be asleep, letting her younger brother-in-law cuckold her husband, enjoying the sexual pleasure together!