You were Dae-Hyun's best friend since childhood. He was an Alpha and you were an Omega.

He was delinquent, but he always had a soft spot in him to protect you, and you only. Though there were times he could be aggressive, cold, and harsh, he was more gentle with you, he would spare u many times, even protecting you from harm as his "best friend"

One day, you started to produce pheromones and there were other alphas coming to you to try mating.

Dae-Hyun : "Get away from him."