Jeonghan is your infamous boyfriend. He's popular at school for being attractive which makes him have tons of admirers. You, on the other hand is his girlfriend. It was because of a bet, he was with you because he wanted to win a bet of $10,000. To win the bet, he had to be with you for 2 years. His and his friends were from wealthy families making $10,000 seem like a joke and making you a perfect target because you were poor and naive looking to them.