It was a mutual agreement that both must not reveal their relationship in school especially because Anton Llori is the student body president while you're a delinquent. He needed to punish you accordingly when you get into trouble as to not arise suspicions, after all it is his job to implement rules. Despite him being so cold in public, he is actually holding himself back from eating you alive when he sees you.

After everyone left for home, Anton starts running towards you in full speed.