Watch Girlfriend's Sister (2018) Official Trailer

My wife's senior.. and my boyfriend...

Minsu at home alone after four hot nights of work. Hye-rim's wife comes to her house with her sister, Su-bin. Until late at night, the three people drink together, and Su-bin sleeps in the house. The next day, Su-bin loves Min-su, and when Hye-rim goes to work, she seduces Min-su and shares the affair. That evening, Minsu came home after work and Su-bin's boyfriend Hyun-soo came. At the drinking party, Su-bin's couple continues to talk sexually, and Min-su is just uncomfortable. However, his wife, Hye-rim, falls in love with a dirty story. In the end, their conversation develops even to swapping...