"Why don't you just go take a swan dive off the roof and pray you're reborn with a quirk in your next life!"
In another universe, Midoriya Izuku goes home that day, and gets attacked by a villain in an underpass. He meets his idol and subsequently gets his dreams crushed by said idol. He finds out All Might's secret, and he unintentionally causes the hero to lose track of the villain. Midoryia Izuku rushes into a hopeless fight to save one Bakugou Katsuki with his terrified eyes and sparking hands as the Pros watched on, useless.
In this universe, Midoriya Izuku fishes (ha! Get it?) his notebook out of the pond and lets out a world weary sigh when he realises there's no salvaging it, letting it plop back to the depths of the pond amongst the koi.
I guess I'm not leaving a note then, Midoriya Izuku thinks, resignedly. He hadn't really wanted to, to be honest, but it seemed like the kind of thing to do. He stands up, sighing, and tries futilely to wipe the grass stains off of his knees. It's not like it matters anyway.
In another universe, paths diverging and splitting off into a thousand different possibilities, Midoriya Izuku will go back to his classroom to find some (preferably dry) paper. Perhaps he will get stopped by one of his teachers who will scold him for being at school after hours and send him home with an unrelentingly stern glare for the small boy. He will walk home uninterrupted (huzzah!) and go on to live a normal, boring life. Perhaps.
In this universe, rather than making another attempt at leaving a note (because who's really going to care anyway?), Midoriya Izuku heads straight up to the roof.
In another universe, the door to the roof is locked shut with a heavy chain and padlock, and Midoriya Izuku is once again set on the path to a normal life.
In this universe, the chain slips easily through his fingers, puddling on the floor at his feet. With a bit of effort, he gets the heavy door open, shielding his eyes against the bright mid afternoon sunshine assaulting his eyes. He steps out cautiously, weirdly calm. His footsteps crunch loudly against the gravel under his feet.
In another universe, a hero — perhaps Eraserhead, maybe even (gasp!) All Might — appears before he even reaches the ledge, concerned at what the young boy is doing on the roof at this time. Midoriya Izuku gets flustered, asks for their autograph and, upon realising he has nothing for them to sign (as his notebook is currently literally swimming with the fishes), asks them to wait while he digs in his backpack for a napkin or something. The hero stays with him until he promises to go straight home, grinning all the while at getting to meet one of his heroes.
In this universe, Midoriya Izuku makes his way slowly over to the edge of the roof, feeling more tired than he has any right to. He takes off his shoes and socks, because that too he feels like the kind of thing one does in a situation such as this. As his bare feet touch the cold floor he is grateful for that at least it will it matter if he gets tetanus. He shrugs his bag, and then his gakuran off onto the floor in a messy pile. Then, reconsidering, he picks his jacket up again and folds it neatly, placing it carefully over his blood-red sneakers.
In this universe, there's no turning back, no errant villains or childhood friends to distract him from his goal, so Midoriya Izuku just tiredly scrambles over the safety railing and onto the small ledge.
"On the count of three," he mutters, the wind pulling at his hair and clothes as if in invitation. He rocks forward on his toes slightly, anticipatory.
One. In another universe, Midoriya Izuku finds something within himself worth fighting for at the last moment, a kind of unbreakable hope. Or perhaps he finds a burning, festering hatred, for quirked society and all the so-called heroes who help perpetuate a society that keeps the weak down and allows the strong to go unchecked. Or perhaps he will dig down and find fear, fear of the unknown, fear of falling from such a large height, fear of never getting to make something of himself. Fear of pain. Fear of leaving his mother behind without answers, he really should have left a note– Whatever it is he finds, it allows him to climb over the railing to safety.
Two. In another universe, Midoriya Izuku decides he would much rather do this at a time when the sun wasn't so glaringly bright in his eyes so that he could look at the city for one last time, and the thought of never seeing his home again, never seeing his mother again, oh god what is he doing, is strong enough to shock him back into his senses.
Three. In another universe — well, you get the picture. In this universe, none of that happens.
Midoryia Izuku jumps.