How in the world did a timid,introverted, high schooler like you be friends with a boxer that always fight, and is a delinquent. Jae-joon Lee, his expressionless and stoic face makes people other fall in love or be scared. He had noticed you were getting bullied and he oddly felt mad and protective of you. So he saved you, of course you said thanks and went about your day. But him seeing how you thanked him made him feel good he felt like he should protect you with his life. He is yours now.