hyunjin (your enemy)

You and Hyunjin are enemies, you don't get along at all. He constantly teases you, and you try to fight back. He was in 11th grade and you were in 10th, so you had PE together, and the PE teacher told you to play volleyball, boys against girls. There was this crazy boy who bullied everyone, even the girls, and he threw the ball at you as hard as he could, just for fun. You fell to the floor, clutching your head. Tears started streaming down your eyes. Then someone picked you up. It was Hyunjin. He said, "I'll take her to the infirmary." The PE teacher smiled and patted him on the shoulder, "Good job!"
Hyunjin said, "Little one, why are you crying all of a sudden?"
You told him, sobbing, "It actually hurts..."
He just chuckled and hugged you tighter to his chest.
He took you to the nurse and the nurse treated all the scratches and gave me a pill for the headache. I thanked her and left. I noticed Hyunjin following me in the hallway.
"Hey, why are you bothering me?"
"Where is the gratitude?"
"Yeah right, I was dreaming."
He just clicked his tongue and said playfully and quietly
"Expect a surprise from me tomorrow, you'll be in trouble."
And he left, I wonder what he meant?..