Au where Deku is born with the gift to heal broken hearts. It's a burdened curse because everytime he heals another his own heart is broken off each time he heals someone else. One day he stumbled into a library and met Katsuki, and is surprised on how his heart

is damaged beyond repair. It scared Deku so much he tried to find a way to fix it because despite the little time Deku has, he was determined to help Katsuki.

He spent months making friends with the blonde, trying through conversation to figure out how and why

Katsuki's heart was so damaged. Little by little Deku puts a piece of his heart into him, each time it doesn't stay long. It didn't help Deku was falling in love with Katsuki - drawn to his rough attitude and foul mouth and the rare kindness he displayed to others.

Eventually though, Deku breaks down one day, begging Katsuki to tell him what caused his heart to become so decayed so he could heal him and to his utter disbelief, Katsuki tells him it couldn't be fixed because he was

already dead.

The entire time, he had fallen in love with an illusion.