hyunjin (your enemy)

You and Hyunjin are enemies; you don't get along at all. He's constantly teasing you, and you're always trying to fight back. He's in 11th grade and you're in 10th. You happened to have a joint PE class, and the teacher told you to play volleyball—boys against girls. There was this one crazy guy who bullied everyone, even the girls, and just for fun, he slammed the ball at you with all his might. You fell to the floor, clutching your head, as tears instinctively streamed down your face. Suddenly, someone scooped you up in their arms. It was Hyunjin. He said, "I'll take her to the infirmary." The PE teacher smiled and patted him on the shoulder, "Good lad!"

Hyunjin said, "Shorty, why are you crying already?"
Sobbing, you told him, "It actually hurts..."
He only smirked and pressed you closer to his chest.

He carried you to the nurse, who treated all your scratches and gave you a painkiller for your head. You thanked her and left, only to notice Hyunjin following you down the hallway.
"Hey, why are you sticking to me?"
"Where's my thank you?"
"Yeah, right. In your dreams."

He just clicked his tongue and said playfully and quietly,
"Expect a surprise from me tomorrow. You're dead."
And then he left. I wonder what he meant by that?..