You don't have to be a hero to save the world.
When Katsuki returned to school, Izuku couldn't believe what he saw. Katsuki's arm, or what was left of it, was bandaged up tightly and yet he turned his chin up and bared his teeth at anybody who let their gaze linger on the now damaged appendage. That was something he had always loved about Katsuki. He was strong, never letting his personality falter even in the worst of circumstances.
It doesn't make you a narcissist to love yourself.
No matter what stood in Katsuki's way, he never backed away. It was a large flaw in the end, but... Izuku adored that about him. He never let anyone get in his way, never stepped back until he won, went to extreme limits to strengthen his body and quirk. Nothing about Katsuki was undesirable to Izuku.
Katsuki began to struggle when the remaining portion of his arm was healed and he could start to train again. He couldn't use AP Shot, Stun Grenade was nowhere near as strong, Howitzer Impact would likely never happen again. Even though he got shit for it, Izuku cheered for Katsuki, calling out that cute nickname he had always used. He believed Katsuki could do anything, even if he struggled.
It feels like nothing is easy,
When Katsuki's prosthetic was fitted, it just drove him crazy. He would often tear the damn thing off, launching it across the room with a well planned blast. When he tried to use AP Shot, he nearly ended up getting suspended for a projectile flying through the air that fast with no warning.
It will never be.
Izuku's chance to show Katsuki how much he loved and supportive of him came when he found the other boy in the locker room. Katsuki's shoulders quaked as he bawled, infuriated sounds leaving his sound as though he were a wild animal caught in a trap.
That's alright.
Let it out.
For Katsuki, this really did feel like being caught in a trap. He could barely do anything worth a damn. Izuku could tell just by studying his body language, and he worked his body into a position so he could hold Katsuki, the other boy's head on his chest. Breathing softly, he nuzzled the top of Katsuki's head, speaking up:
"Talk to me."