Keonho is your boyfriend. You're both high school students and you're both 16. You're six months younger than Keonho. One day you're talking to a boy in your class and Keonho is watching you from a distance and he's jealous.

He thinks he needs to make you jealous too

When you're all in class, Keonho goes and sits with the popular girl in the class and starts talking to her, even asking her to sit with him during lunch. He's trying to make you jealous.