You and Katsuki went back a long time. You'd been in each other's presence since you were just kids-- naive and little, side by side.
Your relationship had changed quite a lot over the years. As kids, you vowed to stay near one another: a silent bond, together through every scraped knee and playground tattle-tale. You were practically glued to each other's sides back then. The two of you had always understood the other perfectly, never needing words to comprehend how the other was feeling. You could tell what Katsuki was thinking just by the look in his crimson eyes, or by the expression plaguing his face. In middle school, however, things changed a bit. It wasn't intentional: it was simply just how things went. Girls stopped being playmates and instead got "cooties." You and Katsuki drifted a bit, warping into different crowds. People crowded him due to the strength of his quirk and his confident demeanor, and you preferred to protect your peace. It wasn't as if you completely forgot one another, though. That much was evident in every look exchanged in the hallways, every brush of your fingertips when passing homework up to the front of the classroom. Your silent bond was still there, just less noticeable than before.
It wasn't until High School that things really changed for the two of you. Physically, mentally, socially. Neither of you addressed it-- not out loud, at least. The two of you grew closer once more, reconnecting after a bit of maturing. Katsuki had become a strong young man, all muscle and power, with a handsome face to match. You had grown into a beautiful young woman, not only strong but unfathomably beautiful. When Katsuki looked at you, he realized there was always a weird, tingling feeling in his chest that hadn't been there before. He assumed it was just hormones, a fleeting feeling that would disappear with the passage of time. He ignored the sensation, claiming he didn't have the time to focus on such a fickle thing.
Eventually, however, Katsuki realized that the feelings he had for you weren't just temporary. They were real, raw, and unavoidable. He didn't want to accept that he, Katsuki Bakugo, had fallen for someone. He didn't do shit like that-- he detested things like crushes and love because they made people vulnerable. He hated vulnerable. But he didn't hate you, and that was the issue. He planned on keeping his feelings hidden for as long as he could: he refused to act on them, because he didn't know where he'd even start. He had never liked a girl before, not before you. And, evidently, his plan had worked. You never suspected a thing. The thought that Katsuki might like you, love you, wasn't even a thought in your mind.
One day, you showed up to Katsuki's dorm. It was late, and he was about to go to bed. You mentioned that you needed to talk about something. Something serious. All he had done was nod and let you in. Then, you dropped info on him that he had never been expected.
"I think I like Izuku," you had said. He remembered what he felt like when he heard the words fall from your lips. He felt like his heart stopped and his blood had ran cold. The news shouldn't have been shocking-- Izuku was kind, thoughtful, patient, and loving. Everything that Katsuki wasn't. But that didn't make it hurt less. If anything, it made things worse. His entire life, he had felt like he was in a competition with Izuku. This meant he lost the competition. And it felt like he was losing you, too.
'Is he all that you want?' Katsuki thought. 'Is he all that you need?'
The next day, he bumped into you and Izuku. You were chatting with the green-haired boy in the commons room, laughing with him. Laughing with Izuku, telling him jokes. Jokes that you used to tell him. Katsuki scowled, for it was the only way his body knew how to react. Katsuki could do better than Izuku. He could build you a house, if only you'd come back to him.
"Tch. Get a room, you idiots. You're pissin' me the hell off." Katsuki scowled, crimson eyes filled with hurt.