Post-game, spoilers. Expanded from a drabble meme, original request by Farli.
For a King, Mickey didn't seem to mind having to rough it. But Kairi's only experiences with royalty involved having her heart taken out by one, or maybe it was someone just pretending to be one, or maybe it had happened long after she'd left her original home. She'd never been too clear about the whole business of Kingdom Hearts, apart from dim memories of people she knew she was supposed to revere. Kings could be scary.
Mickey acted like anyone else though. He didn't like it when peanut butter and jelly got on his nose after sandwiches, but kept claiming that he loved the taste. His voice got all funny and squeaky whenever he was excited -- which was most of the time. He got sand in his shoes and coat just like the rest of them, and hung up his socks to dry when Pluto dragged them through the surf. He bruised and bled and got tired after running too long on the beach, and never once protested any of it.
They had taken refuge on the Island because it was easier than worrying about what people's parents might say if Kairi came back with a mouse, a duck, and a dog. Two dogs. Kairi had explained her own absence on Selphie, explaining that they'd been out on sleepover and working on a school project. A really big one. Really really big.
That was the other funny thing about being involved with Kingdom Hearts. People didn't seem to notice when they'd forget or remember things that the Heartless had touched. Kairi's mother always tried to ask about that nice young boy with the white hair, if he was still away visiting relatives, but then a vague expression would come over her face when she tried to come up with Riku's name and she'd trail off before leaving to do something else.
It made Kairi wonder sometimes. If she disappeared too and never came back, she might vanish with no one to worry where she'd gone. Even someone with a Keyblade wasn't infallible -- Sora had disappeared from her mind, and she'd been hidden in his.
But without any other clues to go on, Kairi was stuck. She smuggled food out to the Island and told her mother that she was busy studying in the afternoons with friends. Goofy tried to give her help with her math homework, but it was Donald who figured out the formulas fastest, snapping out peckish explanations along with demands for Kairi to show all the steps in her equations.
"We could show you magic instead," he squawked one day as he fussed over her textbooks. "What are they teaching kids, it's useless, useless, useless. Why, when I was in classes... "
"We could teach her how to fight!" Goofy piped up.
Kairi glanced over to where Mickey was burying his friend underneath a layer of sand. Pluto had been helping out eagerly between rounds of fetch; Goofy was nearly consumed by the beach, a long bulge marked by two shoes and a head. The King had grit swiped across his chin and one ear.
When he saw her looking, he grinned.
At night, Goofy's legs stuck out from the little canvas tent she'd been given one year for her birthday, but everyone seemed to think it was funny, especially when he stole all the blankets off Donald and snored too loud. Mickey slept out under the stars; he said that he could never get tired of counting them, seeing all the worlds that were being kept safe now, saved from the Darkness.
Every evening, she sat with the King and watched the sun go down.
Once he reached out and gave her an awkward pat on the hand. "He'll come back soon, Kairi. You can count on it. Both of them," he added with a nod. "They're very strong, and I'm sure they'll be able to find their way through whatever they're facing now."
She smiled, squinting against the light that sat like a burning portal on the waves. The sun turned the ocean into fire.
Mickey watched her in silence for a moment before he offered a sympathetic, "It's not always fun to wait, is it?"
"I thought I wouldn't have to again." The confession made her laugh after she spoke; it sounded like the kind of thing a little kid would say, tired and whining from not enough sleep. "This time, I was sure I'd go with Riku and Sora and help keep them okay."
Behind them in the distance, Donald gave a sharp yelp. Pluto tore by, kicking up sand; a blue hat was clutched between his teeth while he made merry laps around them, triumphant with his theft. Mickey made a token swipe for his dog and fell over. He laughed into the sand while Pluto frolicked away.
When the noise receded, Mickey dusted himself off and turned back to her. "It's hard to be the one who's not out fighting," he offered quietly. "You never know what might happen that you could prevent. Sometimes all you want to do is protect the people you care about, but then you're left waiting behind."
She smiled again, but this time it hurt to do so. "So you've done it a lot?"
He shook his head; not to dismiss her, because his eyes were watching the sun and his mouth was aimed at the sea. "Kings have to wait too."
She didn't know what made her ask the next question, but it came out anyway.
Mickey didn't pause. "Which one?"
Kairi looked away, feeling her cheeks flush. She'd wanted to find out what had happened to make so many people chase Kingdom Hearts, but Mickey made her feel ignorant all over again. "I don't know. Either."
He sighed, sprawling out his feet and poking constellations in the damp sand. "When you go somewhere on a long trip, it's easy to lose your way. That's why having a friend is such a big help. That person can show you the doorway back to yourself." Poke, poke, went his finger, until he was drawing happy faces all in rows, spinning upside down and sideways. "Just like I know that no matter where I go, no matter what I fight or how scary it can be, I've got my home waiting for me. All my friends are back there -- Minnie too. That's what helps me go into darkness and not be afraid that I won't come out again."
Kairi watched the pattern of smiles draw itself out on the beach between Mickey's feet. "Ansem the Wise didn't trust what his apprentice could do," the King stated next, doodling the start of an upside-down heart before he caught himself, and flattened his palm over the symbol. "And that led to Xehanort not trusting him. Both of them wanted to understand the heart, but they didn't stop to think about figuring out the one person right next to them. If they had... maybe this would all have turned out different."
She considered this new information with a frown, sliding up the beach to keep her toes from getting soaked by the tide. "So you're saying this all happened because they didn't reach out to each other?"
"Maybe. Yeah," Mickey nodded, wiping the beach clean with his fingers. The sand clumped up and stuck to his hand, so he swapped to using a shoe. "Maybe they didn't think the other person would reach back. Xemnas said that the only thing he remembered a heart could be was full of hate or despair. It makes me wonder what Xehanort must have been feeling, when that man was taken by Darkness."
"And that's why everyone wants Kingdom Hearts so much? Because it's something that can be a friend?"
The guess felt wrong even as Kairi said it, but Mickey accepted her questions anyway. "Sorta. I think Xehanort and Ansem were looking for their own paths out of where their research led, and Kingdom Hearts was an answer. But they only ended up fighting over it. Instead of waiting for each other and helping lead the other person out, they became enemies. It's really a shame."
She didn't know if she understood all of his explanation, but one fact was certain. "Good thing Riku and Sora won't do that," she announced proudly, ignoring the small flickers in her memory that gave her the lie. Go away, she informed them. Those weren't real fights. Not once, not ever.
The King seemed to see those moments, because he waggled a teasing finger in her direction. "Really?"
"Yep. I'm positive." Wrapping her arms around her knees, Kairi leaned back until her heels came off the beach and her balance threatened to tip over. Doing so made her dizzy; she tilted her head up to the sky. "There's no way they'll end up like Ansem and Xehanort. But if they know what's good for them, they'll hurry up and come back before we run out of marshmallows."
"Even kings have to wait," he reminded her, but this time his voice was laughing. "Sometimes it's our turn to stand at the end of the tunnel, shining the light to our friends."