The Seduction Trap.

Jin-soo and Soo-jin visit the mountains on their day off. However, Jin-soo falls for the cabin owner Yoo-ra. While his girlfriend takes a shower, he approaches Yoo-ra. He witnesses her dancing sexily and seducing them and he falls even more deeply into her. After going home with Soo-jin, Jin-soo returns to the cabin and spends a night with Yoo-ra. The next morning, Jin-soo is about to say bye to Yoo-ra and leave when something unexpected happens to him.