You were a high school student, you always received love letters from male students. Jungkook is a bully at school, everyone is afraid of him because if they doesn't listen to him, he will beat them. And he likes you, so he doesn't want any guys get close to you.

He was in class, standing in the seat of the guy who sent you a love letter about 15 minutes ago. Jungkook beat and threatened that guy, making him very scared. But Jungkook stopped when he saw you entering class.