Chapter Text
Atsumu is the older of the royal twins, therefore, he’s the one that has to step up to the throne once the King deems it necessary.
Kiyoomi, on the other hand, isn’t. He’s not a prince, nor a Duque, not even a noble.
He is the youngest son of the Sakusa family, one that has been serving the royals for decades.
Kiyoomi's father is the King's right-hand man, his best friend, whatever you prefer to call him.
He and Atsumu met the first time his father took him to the palace, with the intention of them befriending each other.
It went as horribly as Kiyoomi thought it would.
Hair was pulled, shirts were tugged with the intention of annoying each other, accents were mocked, and things were thrown at each other.
Everything that could’ve gone wrong, did.
Kiyoomi /hated/ Atsumu with a burning passion.
Three years passed and they went from being 9 years old to being pre-teens at the age of 12.
They still annoyed the hell out of each other, bickering about every single thing they deemed possible.
But they also started to tolerate each other, maybe even care.
When they turned 14, Atsumu referred to Kiyoomi as his best friend, even if all he does now when the subject is brought up is deny he was the one to do so.
The title being acknowledged made them tone down the supposed hate they had towards each other.
They still bickered and teased every time they saw each other though.
The year of his 16th birthday, Kiyoomi was declared Atsumu's knight, his official guard, and the person who would remain by his side forever.
Somewhere along the way growing up, feelings were caught. Jealousy and teenage angst happened.
It wasn’t like it was Kiyoomi’s fault when Atsumu would look at him so softly, then flirt with everyone else around them.
They didn’t talk. Or more like not willingly, at least.
Osamu, who was there every time Atsumu wanted to talk someone’s ear off about "how /hot/ Omi looked today” and how it'd suddenly change to “he doesn’t love me. Why would he?”.
So one day, he locked them both in their shared room, and didn’t let them out until they figured their shit out and stopped sulking when their feelings were “so obviously mutual”.
And they did, figure their shit out, that is.
They managed to hide their relationship from anyone that wasn't Osamu or Motoya for a year until someone saw them kissing and told the twin’s father.
It took /a lot/ of talking and convincing for them to be able to keep being together.
No. Atsumu didn’t want to marry a princess just for the sake of an heir. He was barely 18.
No. Kiyoomi wasn’t with Atsumu for the title, he couldn’t care less about it anyway.
After so many pleas from the teens and questions that had nothing to do with their dating from their parents, they were given permission to maintain the relationship as long as they didn’t allow it to get in the way of their duties as future king and knight.
After that, everything went well. Really well.
Until the war happened.
When requests of having Atsumu and a princess from another kingdom married were rejected, said kingdom’s King got mad and later disgusted once he found out the reason of the rejection.
So he did what he considered rational (It wasn’t).
He started a war.
Pretty childish if you ask Kiyoomi, and that's a lot coming from him seeing how the guy he's dating can be sometimes.
And seen as Kiyoomi was a knight, trained to act up in situations as this one, he was told to go.
Atsumu took that personally, of course.
He whined, groaned, and screamed one time, and only when his father screamed back did he stop.
Both of them were scared, maybe a little. The other kingdom wasn’t a very rational one, and they weren’t very fair with their fights either.
Reason as to why other kingdoms try to avoid them the best they can.
And that brings them to the present, the night before Kiyoomi is supposed to leave with the others to try and end the war.
Lost in his own thoughts, he didn’t see Atsumu’s eyes get teary, bottom lip trembling before he caught it between his teeth.
It wasn’t until the sniffles started that Kiyoomi turned to look at Atsumu, sitting beside him in the blonde’s bed.
He pulled the twin closer, circling his arms around him and resting his cheek against the soft hair.
“Atsu? What’s wrong? Talk to me, love.” He didn’t get a response other than hiccups, the result of Atsumu trying to not cry out loud. “Atsumu?”
“You could die there, y’know? You’re leavin’ me, and we can’t know if yer coming back.” He says, burying his head in the curly-haired’s sweater after.
“I’m not, sweetheart. I’ll come back to you. Just like I told you I would if something like this happened someday, remember?”
And it’s true, he did say that.
‘I have to and /want/ to be with you forever, how will I ever do that if I don’t come back to you every single time?’ He had said.
“We don’t know that. You’re leavin’ me.” Atsumu sniffles, voice muffled by Kiyoomi’s sweater.
“’m not, Atsumu. I’d never do that. But I don’t have a say in this, and neither do you.” He pushes Atsumu’s hair out of his forehead and black meet big, teary, hazel brown eyes.
“I was trained to become a knight, to protect you and destroy everything that threatened your life. This is one of those occasions” He tells him, softly, lifting one of his hands to caress the blonde’s cheek with his knuckles, returning it to his waist after a few seconds.
“But ya won’t be here, with me. And who knows when you’ll come back- /if/ ya come back.” Atsumu’s eyes get teary, like he’ll start crying again any second.
Kiyoomi’s eyebrows furrow. “Hey. Atsumu, look at me.” He waits until the mentioned blinks the tears and looks up at him again. “You know I’ll always be here, right? I couldn’t leave you even if I wanted to. Not you.” He tells him, voice firm but eyes so soft looking at the boy in front of him.
Said boy stays silent for a while, lost in thought, before he untangles one of his hands and brings it to eye level, pinky lifted.
“Promise?”
Kiyoomi’s mouth corners curl up in a little smile that Atsumu returns. He lifts his own hand from the latter’s waist, pinky already up.
They go to sleep a while after, arms around each other with legs entangled.
The next day, Atsumu will have to see the love of his life’s figure become smaller and smaller until he can’t see it anymore.
He’ll spend countless nights awake, not being able to stop thinking if Kiyoomi’s okay, alive.
A week after his birthday, he’ll be crowned King without his pillar beside him, and he’ll cry himself to sleep that same night.
Sometimes he will lose hope of /him/ returning until Osamu slaps some sense into him.
But a year and a half later, he’ll learn it was worth it.
Atsumu will find out that Kiyoomi meant it when he said ‘I promise’ the second he sees his figure slowly come closer. The love of his life finally coming back to him.
Just like he promised.
In his black armor, hood already off, riding his black horse, and looking so beautiful that Atsumu can only think about kissing him forever.
Kiyoomi will jump off his horse and inmediately turn to him, arms already open.
He’ll see Kiyoomi smile and he’ll run to him, hugging him with all he has once he reaches him. A kiss shared.
A promise, to not leave each other’s side anymore.
'I couldn’t leave you, even if I wanted to. Not you.'