Izuku doesn’t understand what’s happening at first, and he’s scared. Katsuki is too, he thinks, but he’s only just met the other boy and they only barely touched, and later on, he’ll begin to believe that nothing in the world could possibly scare Katsuki, so he’ll doubt that first impression. They’re both just three years old, meeting for the first time, when there’s a flash of something different that only lasts for about thirty seconds, but it’s enough to startle Izuku to tears.
Needless to say, their first meeting is cut short, because his mother can’t figure out what’s wrong with him. She assumes that the way he sobs about things not being the same to mean that he’s shy about being around new people, and the playdate is rescheduled.
The flashes occur from time to time, and it takes him a few days to begin to understand that it’s color. He knows that he’s supposed to see color when he meets somebody special, but he doesn’t understand why he only sees it sometimes, for a little bit, before his world fades back to the way it was before. Izuku doesn’t tell his mother anymore about it because, even at the age of three, he’s scared that he can’t see color all the time.
Still, he can’t control his curiosity, and the first question he asks her is, “What color is my hair?” And so, green is the first color he learns how to identify.
There’s a second playdate, and his mother is so relieved when he doesn’t burst into terrified sobs upon meeting the new children, and instead latches onto Katsuki immediately. Katsuki, already possessing quite the attitude, doesn’t meet Izuku with quite the same enthusiasm, but they still become fast friends and spend more time alone together than they do with any of the other children.
“My hair is green,” Izuku says. “What color is your hair?”
“I don’t know,” Katsuki says with a scowl. “My mom says all the colors I see are gray.”
“My mom says that it’s bad to tell lies,” he replies, and that makes Katsuki really mad. But he doesn’t know what reason the other boy has to lie; he may be keeping it a secret from everyone else, but he thinks that they should be able to talk about it together.
“Your hair is green,” Katsuki finally says, at the same moment Izuku sees a flash of color. “Green,” he repeats, like he’s trying to commit it to memory. “My hair is blond, which my mom says is a lot like yellow.”
The next time they play together, Katsuki is the one who says, “Your eyes are green too.”
“What color are your eyes?” Izuku asks, excited.
Between the two of them, they’ve learned three new colors- enough colors for Izuku to memorize All Might’s appearance, and they come up with their own names for colors that they haven’t learned yet, but they always keep this to themselves.
Things start to change when they’re four. Katsuki becomes more aggressive, picking on weaker children in the neighborhood. Izuku, who isn’t very strong to begin with, is always the first one to stand up to him, which earns him more and more teasing, as time goes on. They spend less time together comparing colors, and Katsuki starts calling him Deku, and it’s almost as if there was never anything special between them to begin with.
Izuku starts asking more questions about colors to his mother instead, and he doesn’t understand until later that she’s probably already figured out that he can see them, though she probably doesn’t know that he can only see them sometimes. She gives him a book of colors, and, as he learns to read, he learns what each color is. He wants to share the names of them with Katsuki, but he’s almost afraid to now.
Katsuki gets an amazing Quirk and Izuku tags along with him like always, so starstruck that he nearly forgets what they have in common, and all he can think about is wanting to reach him. It isn’t long later that he finds out he won’t get a Quirk of his own and he feels like he’ll never reach Katsuki. They’re barely friends from that point on, and Katsuki wants nothing to do with him, but Izuku doesn’t want to let go of him.
He learns how special soulmates are, eventually, and he gives the book of colors to Katsuki without saying why. Katsuki just looks back at him and says, “They all look like gray to me.”
As he grows, Izuku thinks more irrational things, like that he can only see colors sometimes as a side effect of being Quirkless, and that Katsuki is cursed as his soulmate as a result. Sometimes, he thinks that he can only see colors sometimes because Katsuki treats him coldly a majority of the time. He doesn’t give up on his dream of becoming a hero even amidst all of this, and while he’s in junior high, he begins preparing to apply to UA.
That’s when he finally asks his mother about his condition, because he hasn’t been able to find any reliable sources online, and she says, “You started seeing colors so early, I was a little concerned. But I guess it makes sense, some people do marry someone they’ve known their whole lives.”
Izuku flushes when he imagines marrying Katsuki, but reminds himself that something like that could never happen. Seeing the look on her face now, and hearing her admit she was worried in the past, causes him to hold back, and he doesn’t tell her that he doesn’t see colors completely.
He doesn’t tell All Might, either, when they meet and his entire world is changed. They do discuss it, if only because he uses that as part of his reasoning for being willing to give his life for Katsuki. “But I still don’t understand it,” he confesses, “because there’s not really anything between us anymore besides history. I think I might have done that even if he weren’t…”
He tries to ask All Might about his soul mate, upon learning that he sees colors, but the man just laughs it off and says it’s a little complicated right now. They have more important things to worry about with his training anyway, and Izuku works himself nearly to death a few times, all to make sure that he’s ready in time for the entrance exam.
As he’s tripping, ready to eat pavement and humiliate himself before the test has even begun, the world goes really weird for moment. First of all, he doesn’t fall, and feels like he’s floating, and second of all, there’s a flash of color that doesn’t fade as quickly, and as the girl who touched him lets him down- and he only just now realizes a girl touched him- he sees her, with brown hair and brown eyes and rosy cheeks.
She seems just as thrown as he is, and he thinks, There’s no way , as she regains her composure and apologizes for using her Quirk without asking. Izuku can only stare at her even after the color has faded, and she heads inside without him ever actually saying a word.
The flashes of color come much more frequently while he’s sitting next to Katsuki, but Katsuki shows no sign of reaction, no indication that anything is different for him. Izuku doesn’t understand why he sees more, and for longer, now that someone else has touched him, and he wants to spend more time overthinking it, but the exam takes up the majority of his attention.
When he sees her outside again, preparing for the practical portion, he decides to approach her. He wants to thank her and to get her name, and to maybe ask her if she’s noticed anything different. However, before he can take another step, a hand clamps down on his shoulder and the colors come back into his vision.
It’s a serious, somewhat scary boy he remembers from inside, and he takes a step back with a surprised look on his face. Nearly thirty awkward seconds pass before he clears his throat and resumes lecturing Izuku like nothing transpired, and in all of that time, the colors never fade away.
For the rest of the exam, the colors never fade away, and when he goes home that night, the colors never fade away. Izuku wants to take more time to think on this, to appreciate the fact that he can fully see in color, but he’s so certain that he failed that he isn’t in the mood to appreciate much of anything right now.
The news that he passed, and that the nice girl had tried to help him pick his mood up considerably, but Katsuki does not share that sentiment, and corners him after school one day to confront him. Izuku asks him, “Can you see in color?”
“What the fuck? You’re going on about that again?” he snaps. “That was just a fluke, alright?”
“But do you see in color all the time now?”
“Don’t be fucking stupid,” Katsuki mutters. “You know we can only see in color for about half a minute.”
Well. That answers that question.
There are hardly any sources online that talk about multiple soulmates, and none of them are particularly well-written or credible, which is why Izuku brushed them off in the beginning. Now, however, he isn’t so sure, and when he sees them all together on the first day of school, all three of them his classmates, he wants to get to the bottom of this as soon as possible.
Uraraka and Iida- those are their names- latch onto him quickly, and he’s sure it’s because they’ve figured out that they see color because of him. So, when they walk to the station together, he grabs both of their hands and touch them together, and watches their faces shift between surprise and confusion.
“I think we have a lot to talk about,” he says.
“So, if we can see more, the more people we touch, then how many people are there before we can see colors all the time?” asks Uraraka.
“Actually, I can...I can see colors all the time,” Izuku confesses.
“You can?” asks Iida. “Then that means you’ve got everything all figured out. Not surprising, since you knew before the both of us.”
“So? How many is it?”
“And? Who is it?”
“Uh...you guys might not like this…”
Needless to say, getting Iida and Uraraka to warm up to the idea of having Katsuki as a soulmate is not easy, especially considering the fact that he wants nothing to do with Izuku either. And the three of them keep their discoveries to themselves even as their classmates start to see colors together, none of them sure if they should just go up and touch Katsuki and see where things go from there, or keep quiet.
But there’s the soft, “ Oh ,” from Ashido, when she rests a hand on Aoyama’s shoulder, and a nearly imperceptible shift when Asui and Tokoyami shake hands after being partnered together, and Hagakure apologizes to Ojiro, saying that she still isn’t much to look at, and even though couples don’t form immediately, Izuku can see the changes. And he can’t help but think about how nice it would be to be that close to someone else, and he knows that as long as they keep Katsuki in the dark, he and Uraraka and Iida can’t move forward.
Not to mention the fact that he’s practically been in love with Katsuki his whole life, and just hasn’t wanted to admit it to even himself, considering how absolutely disastrous falling in love with someone like Katsuki is.
Life gets too hectic to worry about it for quite some time, anyway, and if he and Iida and Uraraka can keep pretending that nothing has changed, then they will, until they’re ready to do something about it. Neither of them say how much they wish they could see the world the way Izuku does, and nobody makes note of the fact that Katsuki sees the least of all of them. None of them have to, of course, because they all already know.
Uraraka is the first to bring up the possibility of moving forward. “I don’t think things are going to get better between any of us if we keep it from him. I mean, he’s not that bad lately, you know?”
“That’s certainly one way of putting it,” Iida mutters. “But...I do agree that it’s not fair to keep Bakugo in the dark. There’s no telling how he may react, but if he doesn’t know anything, then we have no way of knowing if this will work or not.”
“It’s not like we have to all date, anyway,” she says, and it’s the first time any of them have brought up the romantic potential of their group. Izuku is glad that Iida’s face goes just about as red as his. “Hagakure and Ojiro are the only ones in our class who have even made it official, you know?”
“That is true,” Izuku says, not sure if this is the right time to admit that he’d like very much to date all of them. “And...I’ve wanted to tell Kacchan for a while. I don’t like keeping things from him…” That’s one hell of an understatement, but he doesn’t go into that just yet.
“So, then it’s settled! Me and Tenya will just run up and slap him on the shoulders!”
“Wh- when exactly did we settle this?!”
“Come on, what’s the worst that could happen?”
“He will probably be very angry!”
“Of course he will! But he probably won’t do anything!”
“ Probably ?!”
“What the fuck are you guys- what the fuck ?!” He’s looking at Izuku as colors illuminate around him, because Iida and Uraraka are behind him, but as they slowly walk to stand in front of him, Katsuki’s eyes widen and Izuku can see that he’s just now registering that the colors aren’t fading.
It’s hard for the four of them to talk about anything at first, because Iida is too flustered and Uraraka is too fascinated with fully seeing the world and Katsuki is confused and angry and very much in denial about this. In fact, days pass in which nothing really changes, except Uraraka trying to get Katsuki to hang out with them, and Katsuki taking the time to tell them why he doesn’t want to hang around them, rather than simply telling them to fuck off and leaving, which is what he normally would have done. Izuku thinks that that’s a step in the right direction.
Even so, settling into a relationship after discovering that you’re soulmates is difficult for most people, and it’s all the more difficult with four people having to work things out, and even more difficult if one of those people is Katsuki Bakugo.
One morning, when they come into class, the color book Izuku gave to Katsuki is sitting on Iida’s desk, with a note that just says, Share it .
“How long have you been keeping this from me?”
“I wanted to tell you sooner, Kacchan. I just didn’t think…”
“What? Didn’t think I’d want to know there wasn’t something wrong with me? That I wouldn’t want to know you can fucking see everything now?”
“I didn’t know it bothered you so much. I didn’t know you cared…”
“What the fuck? I never said I cared, and I’m not some fucking weakling, it never bothered me, Deku.”
“It’s okay if it did, Kacchan.”
“Whatever. You just wanted to have your fun getting all buddy-buddy with them, and you didn’t want me to ruin it. Am I right?”
“No! Not at all, Kacchan. Not at all . You were the first person I ever saw color with, and you’ve always been there, my whole life. No matter what, I always wanted to share it with you.”
“...don’t get so fucking sappy, damn it, Deku…”
But despite his protests, that’s when the two of them share their first kiss.