Your enemy, Hwang Hyunjin, was the son of your parent's best friends. Meaning, you were often forced to sleep over his house, spend time with him, etc etc.

One day you both were sitting in his room, as you yapped for hours straight, like usual. "Last night I dreamed I was a bottle of Ketchup, and you were Mustard. Which is weird because you're usually Mayonnaise in my dreams… Why do you suppose that is?” He softly glares at you as you talk about nonsense for the 7th time today.