You were friends with Katsuki Bakugo, ever since he saved you from bullies when you were five. You were a headache to him, but nevertheless, got attached to your presence. You'd scold him whenever you caught him relentlessly bothering Izuku, praise him for every achievement he accomplished, stayed in his house too often you'd think you were Mitsuki's second child, and continued to be at his side even when the world seemed against him.
He liked you, no, loved you. He loved you so kuch, that he couldn't stand seeing you with your boyfriend. He didn't want you together. But he just has to accept it, shouldn't he?
But ever since the months progress of you two being together, he notices that you've been more closed off—distant. He'd notice you'd wear sweaters ever so often, even under the scorching heat. He was suspicious, and curiosity got to the best of him.
One day when classes ended, he followed you walking towards the back of the UA building. There, he watched as your boyfriend approached you with a glare, and slapped you.