Exchange (2015)

Joon-sik and Min-hee are having a romantic trip to a remote Island. There they stay at a guesthouse of Sung-chul and his sister. While Joon-sik is heavily drunk, Seong-cheol's sister seduces Joon-sick, so Seong-cheol can rape Min-hee. Then a new couple comes and Seong-cheol is caught attacking the girlfriend, and he kills the boyfriend. Joon-sick and Min-hee try to escape.