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It came at no surprise that childhood friends, longtime rivals and hero partners Dynamite and Deku became the greatest power couple on the planet. When they announced their relationship, not a single soul was shocked. Some congratulated them, some rolled their eyes and made comments akin to "It's about time," and most people had honestly thought that they were already together.
They were soulmates.
Not in the literal sense, there were no 'first words' or 'soul marks' in this universe, quirks were bizzare enough.
But anyone with at least one functioning eye or ear could notice. Those two were undoubtedly soulmates, born to live, fight and die alongside eachother.
Everyone knew. Kirishima knew.
So why was it that he'd ever bothered to hope any differently?
Bakugou had entered his life with the same energy he put into everything, loud, with the most demanding presence a 16 year old could possibly have. Bakugou stormed into his life and rearranged everything he saw. He lead by example, and Kirishima would have killed himself trying to follow if he wasn't as competent as he was. As competent as Bakugou showed him how to be. Kirishima admired Bakugou more than enyone else in the world (sans Crimson Riot).
When Bakugou was caught in someone's shadow, he simply made more light. Kirishima did that with his smile, his attitude. Bakugou did that with his fists. It was that difference that made them work as best friends for so long. Now that Kirishima looks back on it, it might have been that difference that made it so Bakugou never saw him in the same light that he saw Midoriya. Midoriya did both. He was just that good. And really, how was Kirishima ever supposed to compete with that? What hope did he have against the Symbol of Hope?
Kirishima didn't think of himself as worthless anymore, (with help from Bakugou of course) but he knew how to be realistic. He knew he was a background character in Bakugous story. His 'hope' was little more than leaning on the small flimsy chance that he would get lucky.
That flimsy chance just got smaller and smaller throughout the years. They saw eachother less and less, rarely hung out, barely even spoke.
It got to point where the only time Bakugou and Kirishima would see eachother, was when Dynamite and Red Riot did and official team up.
"And do you, Bakugou Katsuki, take him, Midoriya Izuku, to be your lawfully wedded husband, to have and to hold, in sickness and in health, as long as you both shall live? "
That didn't stop him from asking Kirishima to be his best man though.
It was an honour, though he expected it. He looked forward to it just as much as the very thought made him want to throw up.
The tears in his eyes were easily mistaken as happiness when he heard his best friend's gruff voice utter the word's "I do," and he was happy to play it off as such.
Now, don't get him wrong, Kirishima was happy that Bakugou was happy. Of course he was! He was just disappointed that happiness couldn't be found with him. And by disappointed, of course, he meant undescribably sad and miserable.
Midoriya was his friend too, at one point. He wasn't as close to him as some of the others, they ran in different circles, but they were friends. Kirishima's not sure when that friendship turned into bitter acid in his stomach, threatening to come up. Every thought of Izuku was laced with the tiniest bit of malice, never enough to seep into his voice, but just enough to make him feel absolutely terrible for having those thoughts.
"You may now unite as one, with a kiss."
Kirishima closed his eyes as Bakugou lowered Deku into a deep dip. He couldn't bare to watch them seal their vows with a kiss, and he hated himself even more for it. As he heard the clapping and screaming cheers of the audience with his eyes closed, he was standing close enough to the center that he could almost pretend it was him. That this was him and Bakugou's wedding, that they were cheering for him, instead of Deku.
Kirishima never wanted to open his eyes again.
An hour or so later, at their beautiful reception, Bakugou and his groomsmen ('men' taken very loosely, as Mina was also included) were taking their group photo.
Kirishima, as the best man, was of course stood right beside the man of the hour. And as Katsuki Bakugou-Midoriya pulled his best friend close to him in a tight side embrace, Kirishima felt as if he'd lost something that wasn't his to lose in the first place.