Fiancee's Sister

After returning to study abroad, Ui-yeon visits her sister Hee-soo's pension with her boyfriend Woojin. However, even before taking a break, Yui leaves on a business trip with the company's urgent call. Meanwhile, Woojin seduces Hee-soo, and Hee-soo, who lived alone, has no choice but to share a fatal love with him. After returning from a business trip, Eui notices a suspicious feeling between the two. What makes it harder for Hee-soo, who suffers between morality and love, is the blatant approaching Woojin. He even decides to give up his destiny and longs for Hee-soo for love. Where will the ending be?