(Wrote this after finishing the game and before seeing the extra ending. Also, probably would take place before we see Kairi and Sora on the log. If you don't know Sora's name is associated with sky, Kairi ocean, and Riku land. So I took it and ran with it and went in the direction of poetic tragedy. Hope you enjoy!)
Sun warmed the spirit as it observed the activity taking place below it and even within it. It stretched on for as far as the human eye could see, wrapping around the earth, protecting it from the sun's well meaning but dangerous UV rays. Clouds spotted it and provided wonderful respite for the humans from the sun when the rays became too much and they could find no shelter. There was a word the humans used to describe the spirit.
Sky. There were different variations of it in all the languages that diversified groups of humans from others.
The sky appreciated the love from the creatures that inhabited the earth, humans and animals alike. There was a dull ache in the stretches of sky that looked over the ocean. It became so intense at times, the sky would try to reach out and connect with the ocean beyond where the horizon split them forever. This resulted in tumultuous destruction unleashed in the forms of hurricanes and tsunamis. The sky would only realize the devastation once the cries of the creatures on land echoed throughout its vast expanse. Then the rain would fall as the sky spirit mourned.
That dull ache only became worse as the sky witnessed the trash thrown into the ocean and the way the creatures took the ocean for granted, with more preferring to explore the sky and the lights that shone brightly beyond the sky. It had to help the ocean. There was a way.
The islands. A friend, the spirit of the earth itself, had created them long ago so the spirit of the sky might have some respite from its distress. It was there that it learned the ocean had been waiting and longing for the sky just as much. The spirit of the earth allowed the spirit of the ocean to take respite among its island shores as well, hoping the time would help the two distressed spirits sort things out.
It was there the spirits took on human forms and the spirit of the sky took on the name Sora while the ocean's spirit also took on a human form and became known as Kairi. Riku, the earth spirit, was the oasis the sky and ocean needed. The spirits forgot what they were and where they came from as no spirit could ever be fully contained within the bounds of a human body.
Sora was blinding with his bright optimism just as the sky could sometimes blind a person when allowing the sun's rays to filter through. Kairi was reserved and calm like some of the beaches the ocean lapped against. Riku was always torn between wanting to help them and knowing their fates would never allow it as one couldn't fight destiny. His human form might have forgotten he was once a spirit but his spirit remembered and mourned over the bleak reality causing Riku to make questionable decisions, but he was always forgiven. Riku's heart always ached as his spirit had trouble adjusting to humanism. He'd seen the wars of the world, how the humans treated it like a game of chess. How they used both the sky and the ocean for battles until the waters ran red and bodies fell from the sky. The earth spirit had its own experiences as a piece on the chessboard.
It upset the spirits; they wanted to restore the hearts lost in the wars even the ones that didn't think they could be saved. Even as humans, the sky and the ocean gave all of their beings to other humans. Riku sat on the beach of Destiny Islands, the island sprung forth from the earth's desire to help the sky and ocean. He knew, as had the spirit of the earth, that the sky could only watch over the ocean from above just as the ocean could only reach out to the sky but they could never truly meld into one. He watched as the sun dipped below the horizon, the only other thing that connected them together besides the earth itself. He remembered the longing looks in both Sora and Kairi's eyes as they would watch the horizon, willing it to twist or change their fate, to let Sora's tight grasp on her hand be enough.
But just as the ocean always slipped away from the sky unintentionally, Kairi's hand always slipped through Sora's fingers just as water would.
Riku closed his eyes and breathed in the salty ocean air around him, feeling the presence of his lost friends practically embrace him. "I'm sorry, Sora. Kairi. I tried. I wished it would have been different. I tried to twist fate for you both." There was a moment of stillness where the sounds of the early night quieted and the waves of the ocean vanished, creating an eerie scene. Then a flash of lightning in the distance, the clap of thunder reverberating around the earth, and the ocean's waves washed further up the shore until Riku was standing ankle deep in it. He knew he was forgiven just as Sora and Kairi had been quick to always forgive him. He also knew the two would never give up, they would always fight their fate and reach out to each other. They were the sky and the ocean. They were Sora and Kairi.
"I've been having these strange dreams lately. Like is any of this for real or just a dream?"