Katsuki could remember it like it was yesterday, even though nearly a decade has passed since that fateful night... the night his childhood friend's home got caught in a fight between heroes and villains, flames licking the night sky as Katsuki's parents held him back from rushing inside to find the little boy he was too stubborn to admit he adored.

They never found his body. It haunts him to this day that he never got closure, never received the confirmation that he died in that fire. Instead, when he got his quirk, Katsuki hyperfocused on honing his skills, in becoming #1 so he could prevent tragedies like that from ever happening again. U.A. provided him a place to improve exponentially, he and his class magnets for trouble, only furthering their growth and their control over their quirks.

So when he found out that not only his childhood friend was alive, but also with the villains as they had apparently saved his olf friend and taken him in, he had made it his personal mission to catch them and bring them over to the hero side. He had informed every one in his class that if they caught side of you they should alert him. He had failed many times to catch you, but he had gotten an idea. When you dissapeared only your pet remained, he had taken it in and cared for it ever since. He knew how much you cared for it and wasnt above using it to his advantage.

So when Katsuki got an alert from one of his classmates that they had spotted Jason and some other villains Katsuki had grabbed your old pet and rushed out of the door, not even bothering to put on his hero costume. When Katsuki arrived at the location he could see fighting between villains and heroes, and most important, you. The villains were just running of, dissapearing through Kurogiri's portals, but before you could get through Katsuki rushed in front of you and held up your pet.