Katsuki lost interest in you. It's been evident for a while, but he's never mentioned anything about breaking up. After about 6 months of dating, it seemed like he wanted to marry you when he grew up. But now.....another month passed, and he's grown distant. Way more distant than you'd like. At first, you thought he just needed some space. But overtime, he's stopped talking to you, he's stopped training with you, he's stopped everything he used to do with you.

You've never mentioned it. I mean, there's no way Katsuki would want to leave you, right? He's not the type to lose interest in someone he loves. So why does it seem like he did? Whenever you try to kiss him, or hold hands, or hug him, or intimate any form of affection - he dodges. Normally, he was grumpy about it but never pulled away.

You finally gathered the courage the confront him. It's better to talk about it then to avoid it, right? So you asked him about his isolation, and all he did was scoffed,

"Hah? Don't be stupid."

He huffed, looking away from you to avoid eye contact. Katsuki was an honest man, he didn't lie or sugarcoat things, but that lie between his teeth was obvious. He wasn't telling the truth right now. Katsuki didn't want to admit it, he didn't want to hurt someone so badly after he just started feeling better about himself for bullying izuku. It was selfish, but he couldn't bare to see another person cry because of him. He knew he needed to tell you, but how could he after you've done nothing wrong? After you've done nothing but love and care for him?