this is just a story explaining how Terra and Aqua affected Riku and Sora's lives (and more importantly, their roles in Kingdom Hearts) so, uhh, yeah. Uses two short flashbacks from Birth by Sleep. does not contain spoilers (unless you haven't played KH1)
"In your hand, take this key. So long as you have the makings, then through this simple act of taking… it's wielder you shall one day be. And you will find me, friend – no ocean can contain you then. No more borders around, or below, or above, so long as you champion the ones you love."
He stared at the man before him, not quite sure if he was serious. The man looked very serious. Slowly, he reached out and grabbed the blade. Nothing extremely exciting happened when he touched it. There was only silence.
"Riku!"
He gasped, and let go of the blade. Sora was yelling at him from the dock.
"C'mon! Hurry it up!" Sora shouted
He smiled and waved at Sora.
"You've got to keep this a secret, okay?" the man said, drawing his attention. "Otherwise, all the magic will wear off."
Riku nodded, and the man chuckled and ruffled his hair. Riku laughed too.
Riku woke up rather quickly. He rubbed his head, a bit confused. That dream, it was… it was a memory. A memory from long ago. How long had it been? Five years now? It felt like longer. A lot longer.
He casually glanced out the window, looking up at the sky. The outside world, that key, all dreams of long ago. But, he would like to get to the outside world, someday. Especially after she arrived, four years ago. Ever since Kairi arrived, well… it got him thinking. If she had come HERE, then couldn't they LEAVE?
He sighed. What he wouldn't give to see the outside world. And once he got out there, he could get stronger. He picked his wooden sword up off the floor and swung it around a few times, laughing to himself. Not that he really needed to be any stronger, he was already the strongest on the Island. But, who knew how strong the people in the outside world were? They were probably much stronger than he was.
"I'll find out one day," he told himself, thrusting his sword into his pillow, as if it was an enemy to be killed. "No ocean can contain me forever."
XXX
And five years later, his chance came. He got the chance to go the outside world. He took it in a heartbeat, not wanting to stay on the Islands any longer. It was about time he got out of that stupid place. Ten years ago he had been promised that he would make it to the outside world, and it was finally happening. His dreams were finally coming true.
Until, of course, Sora started showing off his new Keyblade. It took Riku a while to realize it, due to the event happening ten years ago and the memory was fuzzy by now. But the Keyblade that Sora was carrying around was rightfully his. How did Sora end up with a Keyblade anyways? He was stronger than Sora, wasn't he? He had always been the strongest, why wouldn't he be now?
"It all ends here!" Riku jeered, staring at Sora. Sora held the Keyblade, his Keyblade, in his hand, as if it belonged to him. As if it was rightfully his. He laughed at that thought. Sora wouldn't have the Keyblade much longer. "There can't be two Keyblade Masters!"
"What are you talking about!" Sora shouted, obviously confused.
Riku smirked. Sora couldn't see it coming. "Let the Keyblade choose…" he laughed, reaching out, "It's true Master!" He concentrated hard on the Keyblade. Sora gasped, as the Keyblade started to wrench itself out of his hands. He quickly grabbed onto it with his other hand and tried to keep a hold of it. Riku smiled, Sora could resist all he wanted, but he wasn't going to stop it from happening.
After a bit of struggle (maybe a bit too much, Riku couldn't help but think) the Keyblade tore itself out of Sora's hands and appeared in Riku's outstretched hand. He grinned. Sora and his friends were absolutely dumbfounded.
"Maleficent was right…" he said, mainly to himself. She had been the one that had reminded him. Reminded him that the Keyblade was rightfully his. "You don't have what it takes to save Kairi!" he sneered. "It's up to me. Only the Keyblade master can open the secret door… and change the world."
"That's impossible!" Sora shouted. "How did this happen? I was the one who fought my way here with the Keyblade!"
Riku laughed. "You were just the delivery boy," he sneered, grinning. "Sorry, you're part's over now." He paused, and then his grin grew wider. He pulled out his old wooden sword and tossed to Sora. "Here, go play hero with this," he said, and then turned and walked away.
XXX
Sora stared at the wooden sword in shock. He crumpled to his knees. What had just happened? The Keyblade, torn from him, and Riku-
Oh Riku…
And to make it all worse:
"C'mon Goofy, let's go," Donald said. "We have to remember our mission."
"Oh!" Goofy paused, and then continued in a quieter voice. "Well, I know the King told us to follow the key and all… but…"
"Sora, sorry…" Donald muttered.
And the sound of their footsteps echoed into the silence. Sora didn't hear. Sora wasn't paying attention. All that was going through his head was the image of Riku's back as he walked away, Keyblade in hand. That image, and a voice. A voice he hadn't heard in ten years.
"If something happens, and, Riku's about to get lost – or say, he starts wandering a dark path alone – you make sure to stay with him and keep him safe. That's your job Sora, and I'm counting on you to do it."
And it was that memory that made him get up and continue fighting. And fighting. And fighting. He had to keep Riku safe, no matter what. It didn't matter that Riku kept yelling at him. It didn't matter that Riku kept throwing insults at him. He promised to keep Riku safe. And that's just what he was going to do.