I know this is kind of a crazy idea for a crossover. After all, Kingdom Hearts and Fullmetal Alchemist are so different. I really think I can make it work, though, and I hope the way I'm doing it makes sense. It'll be a few chapters until the actual crossover part starts, so just hang in there. Just a disclaimer, though - aside from that 100 Themes one-shot, I've never written FMA fanfiction before. However, I love the series and I think I can figure out any minor details as I go along.

I should also mention that the Fullmetal Alchemist part of this fanfic is set during the timeskip at the end of the series. Because of this, it will obviously contain lots of ending spoilers. For this reason, I highly recommend that any of you who haven't finished reading the manga and/or watching Brotherhood should avoid reading this.

Anyway, enough with that. Here's the story - hope you like it!

"Sora, what does it say?" Kairi asked.

She and Riku waited eagerly for their friend to finish reading the letter. It didn't take long. Sora turned around and looked at them. "It's from the King," he said, sounding somewhat surprised.

"Mickey knows where you live?" said Riku, a little skeptical. "Didn't you say you found this in your mailbox?"

Sora nodded. "It's definitely from him, though. He wants you and me to go to the castle. There's something important he needs our help with."

Riku sighed. "It's been what, two months since we got back? Is it really that urgent?"

"If it wasn't, he wouldn't have sent it to us," said Kairi.

The three of them sat on the front steps of Sora's house, thinking about the situation. Kairi leaned over, trying to read the letter. "How are we going to get there, anyway? We don't have a Gummi ship," she continued.

Sora took another look at the letter. "It says that they'll send someone in two days. We should be able to work out the details before then."

"Two days?" Riku repeated. "That's not much time."

"Well, we do have next week off from school," Kairi said, thinking out loud. "That's good – you two can't afford to miss much more."

"Who says this will take a week?" Riku reminded her. "It might take longer."

Everyone was quiet again. "So we are going, right?" asked Kairi.

"Sora and I are going," said Riku. 'If this is an important mission, it's probably dangerous. You're still really inexperienced. You haven't been in a real fight since your first time at the World that Never Was. We can't afford to put you in unnecessary danger."

Kairi looked disappointed, shifting her gaze towards the ground. "I guess you're right…"

She paused, suddenly appearing excited. "Can I at least come to the castle to find out what the mission is? Even if I just went home after that, I still want to know what you'll be doing."

Riku looked over at Sora. "What do you think?" he asked.

Sora shrugged. "There's no harm in that, I guess."

Kairi thanked him, and looked over at the door behind them. "We'll have to ask our parents about this," she said, a hint of concern in her voice.

"Tell them about it," corrected Riku. "We don't need their permission. If we need to leave, then we will. Simple as that."

Sora nodded. "Yeah, but I think they'll understand."

Riku stood up. "If that's all, then we'd better let them know. My mom should be home by now, so I'll go talk to her. You guys should go do the same."

"Got it," said Sora.

Sora sat on the couch with both his parents looking straight at him. They seemed shocked, and more than a little nervous. "That's what it said," Sora concluded, trying to compose himself. "I can show you the letter if you want proof."

His mother let out a deep sigh. "How important is this?" she asked. "It feels like you only just came home. Do you really have to leave again?"

"It's important," said Sora, firmly. "The letter made a point of saying so. Besides, I don't think it'll take nearly as long this time."

"I would hope not," his father said. "Akemi is visiting next week, remember? She isn't going to be happy if she doesn't get the chance to see you."

Sora recalled his dad telling him about this a few days ago. His sister was several years older than him, and was attending a university on another island. Come to think of it, he hadn't actually seen Akemi since before the islands were attacked. He didn't want to miss a chance to see her again. But the mission…

"I'll see if I can get back before she leaves," he said. "I want to see her too, but this sounds like something we have to do. I'm sorry."

His mom gave him a strained smile. "If it's your responsibility to do things like this, then we really have no right to stop you."

She stood up, and walked towards him, putting a hand on his shoulder. "But please, be careful. Don't take risks that don't need to be taken. And make sure that you and Riku watch each other's backs."

"Of course. Trust me, I'll be fine."

The next day, the three of them met up after school. Sora explained what his parents had said. Riku followed, saying that his mom just wanted him to be back before the break ended. "She was pretty pissed that I had to repeat a year of school," he explained. "She doesn't want me to miss anything more than a few days."

"She seriously didn't mind that you're going out on a dangerous mission like this?" asked Kairi.

Riku shrugged. "She didn't care much about the whole raft thing, either, as long as we didn't get lost. I kinda wonder if anything would worry her."

"She was pretty upset when she found out that you'd let the darkness get the best of you," Sora said quietly.

For a moment, nobody said anything. "Anyway, Mom was pretty worried, even though I probably won't be coming along," said Kairi, breaking the silence. "She kept asking all these questions. Like, if I knew who's taking us to the castle, and if I had a sure way to get back."

"Sounds pretty typical of her," said Riku. "What about your dad? What did he think?"

"He said if it was any other two guys, he'd be worried," she said. "But since it's the two of you, he knows I'll be fine."

She looked over at Sora. "He also wants to know whether I'd be able to handle a real fight," she continued.

"You're not going on the mission, though!" Sora protested.

"He still wants to make sure you've been teaching me well. Just in case, you know?"

Sora nodded. "Just tell him that you've been learning fast," he said. "You're still inexperienced, but you'd probably do OK if you had backup."

Kairi smiled. "You think?"

"Yeah. You're getting pretty good."

"Got it!" Kairi said, cheerfully. "I'll be sure to let him know."

Over the rest of the day, Sora found himself becoming impatient. He'd been glad to be home, sure, but there was a part of him that missed traveling between worlds and meeting people. Now that he had a chance to do so, that part of him was getting excited. He didn't know what he'd be asked to do, but he couldn't wait to find out.

The next morning, the three of them met at the dock, and took their rowboats out to the smaller island. The letter had said to meet there, since no one lived there and no one would see them be picked up. Today the seas were calm, and it was an easy ride over.

When they reached the island, it became clear that they'd arrived early. There was no one there, as usual. "Looks like our ride isn't here yet," said Sora.

"You thought they'd be here as soon as we arrived?" remarked Riku.

Sora looked a little surprised. "Well, no…"

He looked out to the ocean. There were other islands further out, but they were too far to be reached by rowboat. They weren't visible from here, either. At the omment, the sky was clear, with hardly any clouds to speak of. It was a perfect day.

His appreciation of the weather was quickly interrupted. "What should we do while we wait?" asked Kairi.

Sora turned towards her. "I don't know," he said. "Did you bring anything?"

She hadn't. Neither had Riku. None of them had any idea how to pass the time. So for a while, they sat there on the sand doing nothing.

Finally, Kairi came up with something. "Sora, when was the last time we had a training session?" she asked.

Riku gave her a confused look. "Training? Now?"

"Yeah. I want to practice," Kairi told him. "Besides, it'd be something to do while we wait."

She looked over at Sora. "What do you think? You up for it?"

Sora shrugged. "Sounds good to me. I'll go get the weapons."

He ran off towards the old beachside shed, leaving Riku and Kairi alone. "Kind of an odd way to pass the time," Riku said.

Kairi gave him a confused look. "What? You don't want me to keep practicing?"

A slight smile appeared on Riku's face. "It's not that. It's just weird to think that you're so enthusiastic about this. I mean, when we were kids, you didn't like to watch Sora and I play with the wooden swords. You were afraid that someone would get hurt."

Kairi smiled back. "Yeah, I remember. I'd always be looking for shells, or something. And then when you were done, I'd give an extra to the winner."

"Which was usually me."

"Usually. But you know, we're not little kids anymore. I'm not afraid anymore. Sure, I worry about you guys, but I know you're pretty tough. You can handle yourselves just fine."

There was a pause, and then Riku spoke up. "It's not like I don't want you to learn," he said, sounding a little annoyed. "If I was that concerned, I wouldn't have given you that Keyblade I found."

"Exactly. Which is why I have to use it. I'll be in more danger if I can't fight back. Right?"

Riku waited a few seconds, not sure what to say. Finally, he spoke again. "Yeah. That's true."

Before either of them could continue, Sora interrupted. "Back," he announced.

He handed Kairi a simple wooden sword. Like all the ones they'd made and used over the years, this one was well-worn, covered with dents and scratches. "Ready when you are," he said.

Kairi took hold of it. "Ready."

It wasn't too long before their ride arrived. Riku was the first to spot it. When he brought this to Sora and Kairi's attention, they quickly ended their practice session, and the three of them watched the ship draw closer.

As it approached, Sora recognized it as the one that he'd used with Donald and Goofy on their travels. It had been modified somewhat since he'd last seen it, but it was still recognizable. Eventually, the ship landed a little further down the beach, spraying sand in all directions. Sora, Riku, and Kairi ran towards it. As they came to a stop next to the ship, the door on the side began to open.

Donald stood in the doorway, looking out at the trio. Sora grinned. "Hey!" he shouted. "Good to see you!"

Donald nodded. "Been a while, hasn't it?"

He looked over at Kairi. "She's coming too?" he asked. "Sora, the King only asked for you and Riku."

Kairi stepped forward. "Would it be OK if I just came to see what the mission was?" she asked. "I could come back here after that."

Donald gave it some thought. "It's probably alright."

He looked over at Sora. "You guys better be ready. We don't have all day, so if you want to talk, we'll do it on the way there."

Sora gave him the thumbs-up. "We're ready when you are!"

Well, that's the first chapter. I know this one wasn't particularly interesting, but the second chapter is when it starts getting somewhere.

By the way, those of you who are familiar with my stories might remember that I'm really inconsistent about updating. In an attempt to remedy this, I've decided to be two or three chapters ahead of what I post. That way, if I have a dry period, I can post the chapters I've already written. However, I want to try and see this story the whole way through, so hopefully any dry periods will be brief. I have the whole story planned out, so I know for sure where this is going.

Anyway, the next chapter should be up pretty soon. If you liked this chapter, I suggest you keep an eye on this story.