Pretty Young Sister 3: Newly-moved Yoo-jeong had a housewarming party. So-hyeon and Min-soo gather their friends at the housewarming party and meet for the first time. Yoo-jeong falls asleep alone, and Min-soo secretly kisses Yoo-jeong. So-hyeon, who finds out, threatens Min-soo and plays with him. Min-soo had no choice but to accept So-hyeon's terms. Yoo-jeong misunderstands them. But in the process, Yoo-jeong herself finds herself interested in Min-soo. Recognizing that, So-hyeon gives up the room he originally intended to live in to Min-soo and leaves.