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Katsuki had first head of a soulmate from some random girls in his elementary class. They were huddled in that usual irritating way and were giggling stupid, as if they knew better than anyone else. Cupping their hands as if they were being discrete while swapping secrets. And then, he heard it.
"Mommy told me about soulmates," one of the extras had said. "She says they are people who you fall in love with at first sight!"
"Well my mommy says they are people who will never leave your side!" another chimes in.
"My mommy says its someone who you can't live without!" another... Katsuki decided he didn't care anymore.
"Do you guys ever shut up!"
He was a little taken aback from the offended gasp from the group, a few of them whispering harshly about how offensive Katsuki was being. He rolls his eyes, stuffing his hands in his shorts and striding towards whatever the other guys were doing.
It was a conversation that, much like any other of those he'd had around a similar age, he thought he'd forget completely, lost in the midst of time.
Cue Izuku Midoriya, a random person in elementary that seemed to always want to be around him. He thought, for a while, that his company was comforting, and he actually enjoyed a lot of the time he spent going on expeditions with him.
It was only after one was gifted an incredible quirk, whilst the other was robbed of one completely, that Katsuki realised he was many leagues above Deku. He had what it took to be the greatest hero of all time, whereas Deku was just... Deku. A quirkless loser.
Katsuki tried cutting ties. He hated the way Deku kept looking up to him, and yet also kept looking down on him, as if Katsuki were the one who needed help? Katsuki felt embarrassed, pushing him down, beating him up whenever he could to teach him a lesson. Katsuki knows better. Katsuki is better.
And yet, somehow, he could never shake the idiot off.
The rain was hitting hard, slipping down his back and soaking into his hair, bangs sticking to his forehead. Even now, Katsuki still has to wonder how Deku, of all people, managed to get into UA with a barely-cultivated quirk. He couldn't answer it then, but he could answer it now.
It was a private moment he had with All Might, around the time where Deku was practicing with black whip. He asked him how Deku managed to pass, only for All Might to laugh in that wise way, giving a bright smile.
"You know, in the staff room, we always comment about how the two of you are complete opposites to one another," he laughed with a gentle kindness.
"Just get to the point," Katsuki rolled his eyes, though with no sense of irritation. He had been getting better at that.
"He didn't score a single attack point, but received 60 rescue points."
Ah, he thought to himself. It made sense. And that was how he slowly began to piece things together.
He looks at the boy in rags, hiding behind a broken mask, a tattered hood and a heavy layer of dirt, greying the homely greens of his costume. Maybe his eyes were as devoid as his voice, absent and grey, filled with those mutters that he was too tired to say out loud. How he was fighting with all his strength to win.
And how desperately he needed Katsuki to save him.
He knew that the two of them were seen as a pair, despite them never once really hanging out at school. They were both pillars for their own beliefs, both still connecting to All Might, who knows that all too well. Probably why he's so proud every meeting he had with them. Katsuki's desire was to become the best, fight and win against as many villains as he could. It didn't take much to realise Deku's was to save people with a smile, and assure them that it will be okay in the end.
Right from the get-go, one's flaws was the other's strengths. And, somehow, they meet in the middle, at first in the way that two opposites would fuel their own fires to fight, but then as the two polls of a magnet, pulling each other onward.
Deku learnt how to be stronger. He used that nerd brain for battle strategies and techniques, training to the bone to grasp information in the shortest amount of time. He never realised, at least until All Might told him in person, that strength is once of the necessities to become one of the greatest heroes.
Katsuki had plenty of that, and he exercised it on innocent people in his elementary, less so in middle school. He has talent, and there isn't a single person that denied it, making him perfect for defeating villains. And, yet, if there was one thing he was taught at UA, it was how unheroic he is. How bad he is at reassuring people, helping those caught in the cross-fire, how merciless he was at fighting. His first battle with Deku was brutal, and everyone watching felt incredibly uncomfortable. No one bothered to talk to him for a few long days.
But he learned, even as one of the best fighters, that he was not suited to become a hero. And, slowly, he could feel himself become a better person. He could only connect that to his friends who both taught him everything he needed to know, and helped him get a healthier and more comfortable position in the class. He only then realised that, for the first time in many years, he was happy. Truly happy.
They really did complete each other, seeming to shoulder one of the responsibilities All Might had to hold up with both of his hands.
Yet, Katsuki could feel Izuku's pillar crumbling under the pressure that he'd only recently learned to deal with. And he could finally understand what Izuku had said all those months ago, when he was being suffocated with sludge and those piercing eyes gazed straight at him with heroism that he had been searching for every step he had taken through UA.
He looked like he needed saving.
"I promise, I'm fine."
Katsuki was surprised how well he could read Izuku, seeing past all the prejudice and hatred that he had built around himself. Maybe it was from all those joint training sessions, or maybe it was what he had gathered over the many years growing up beside him.
Was now the time to give him an apology? Their relationship was a complicated one - one that not even he could describe in words. Their dependency on one another shouldn't be possible with the way Katsuki had treated him in elementary school; in middle school. But Izuku seemed fine with it - with Katsuki entering his life once again. Which, very slowly, made Katsuki more redeemable. He could now properly atone by supporting Izuku with all that he could.
But the entire time, they were ignoring the truth of their past - how messed up it had been, and how easily forgettable it is now. But Katsuki wanted to show Izuku his progress. How he had gotten better, just as Izuku had. How, even despite them being nothing like each other, the tables had turned at that point.
"I mean it, Izuku. I'm sorry for everything I've done."
Izuku starts mumbling and, through the downpour, he strains to make anything out, but is attentive to the spasms of his muscles, or the wobble of his knees, on the verge of passing out. Katsuki second-guesses himself. Maybe he was just tired. Attacking the rest of his class had taken a toll on him, which is why he no longer had any fight left. Maybe whatever connection they had wasn't really there, just his mind playing tricks on him. Still, he rushes faster than anyone else could, catching Izuku in his arms as he goes limp, passing out.
And he can't explain it but feeling Izuku in his arms was almost like he was supposed to be there. He fits too perfectly.
Somehow, his brain decides to conjure up that conversation he'd overheard from elementary. Fate is just an excuse to explain coincidence. It is stupid, being 'destined' to meet 'the one', and suddenly feel more complete around them. Tying yourself to one of the billions out there. It sounds so fantasy, much like becoming a superhero before the first quirk became manifested.
And yet, Katsuki could never feel more complete than he does around Izuku. All his thoughts, all his feelings, almost his entire life revolves around Izuku. It all goes back to him.
Soulmates.
He looks across to the sleeping bundle of blankets beside him, as the film continued playing out to the class, the solitary blue glow from the screen catching to those delicate lashes, the soft splay of freckles across his cheeks, the usual rosy blush and the handful of curls spilling across his forehead. And he smiles.
You're my soulmate, Izuku.
There is no one else that could pull on his strings as much as Izuku did, meddling and tangling into them. Katsuki wouldn't have it any other way.
And, as legs begin to curl around his own, their hands lacing together under the blankets and that mess of curls slowly falling to his shoulder, he could tell Izuku felt the same. They could start here - something new and fresh, filled with support and care and love. And they will become the best the world has ever seen.
Dynamight and Deku.
The wonder duo - twin stars - childhood friends - the heart of 1-A.
And soulmates.