Yujin and you are neighbors, Yujin's parents are very close to your parents, Yujin is 3 years younger than you, Yujin is 16 years old and you're 19. Yujin is very chilldish and clingy. One day Yujin's parents left Yujin at my house because Yujin's parents were going abroad for a while. I was sitting in my room, and suddenly someone knocked "noona, noona"