This is the "what if" scenario from TWI1IGHTMAST3R's fanfic called Kingdom Hearts: Light and Darkness after chapter 17 where Sora and his companions stay still, instead go to the other worlds to find Terra.
After foiled Hades's new plan and recovered Zack's sense from the Lord of the Dead's control, Sora, Kairi, Riku , and Aqua walked away to find Terra in another world. However, just before any of them could summon the Keyblade Glider, Phil the Satyr called them while running to catch up with them.
"Hey-hey, wait a minute don't go yet, will ya?" The half goat man said, trying to catch his breath after ran with his short legs.
"Huh, what's wrong Phil? Did you forget something?" Sora asked.
"I haven't seen all of yer performance yet. Then I have many new matches for ya, so whaddaya say? Interested?" Phil asked the four Keyblade warriors as he rubbed his goatee as usual.
They looked each other before they could accept or not, they knew that Aqua really wanted to find Terra as soon as possible, however Aqua thought different, she realized that with Xenarot's revival, sooner or later they would face even stronger enemies that they might never imagined before. 'Hmmm, maybe staying here a bit longer will be okay, besides I wonder how far that they have progressed' Aqua thought while looking at the Destiny's Islands trio. After a moment in her thought, Aqua finally decided.
"Hey, maybe we can stay here a bit longer." Aqua said to the three, making them surprised a bit.
"Are you sure, Aqua? Don't we want to find Terra first?" Sora asked.
Aqua nodded, knowing that he would react like that "I want to, but as we know, our enemies are getting stronger as the time passes. So, maybe we could train here to improve our fighting and magical skills."
Riku couldn't agree anymore as he nodded his head "Well, I don't mind about that, besides I want to show Sora how far I've progressed while he was sleeping in Yen Sid's tower." Riku jokingly said, making the spiky brunette Keybearer sighed and rolled his eye at his old school mock.
"And I want to show you that I'm not the girl who needs the protection anymore, I can handle myself this time." Kairi said, agreeing with Riku, although Sora was a bit unsure as he didn't want Kairi to get hurt, considering the enemies in the Coliseum arena were much stronger than usual.
"It's settled then. Now, here are the menus for ya, heroes." Phil said, and then showed them the matches list from a rolled papyrus paper. The matches consisted of:
Rock Titan Cup
Ice Titan Cup
"I'll take the first one, Cerberus Cup." Aqua said, after looked the list for a while.
"I'll take the Rock Titan Cup." Riku said next.
"Then I'll take the Ice Titan Cup." Kairi said too.
Didn't have any choice left, Sora choose the last one, the Unknown Match
"I guess I don't have another choice, so I'll take the last one." Sora said while scratching his head.
"Well, to tell ya kid, I also don't know anything about this Unknown Match thingy, it just popped up on my list by all of sudden." Phile replied while rubbing his chin "But who cares, at least every one of you got one game, right?"
Not too far away, Hercules, Zack, and Meg approached them all "Well, the match will start by tomorrow, so maybe you better rest now or train with Phil." Hercules said.
"And I'll cheer up for you guys too, especially you Aqua." Zack exclaimed then winked at Aqua at the last part, making her face slightly blushed.
"Man, Zack you haven't changed a bit, I see." Hercules said and chuckled at Zack's behavior who always wanted to make out with every woman that he met. Even after more than ten years passed, he was still the same old Zack that Herc, Phil, and Aqua knew.
"And you too Wonder Boy." Zack replied with a mocking grin, remembered the nickname that Meg gave to call Hercules.
As they walked away from the coliseum gates, unknown by them, someone was watching them, especially Sora and his friends. It was none other than Hades, the God of Underworld who wanted a revenge for Sora for failing his plans many times in the past.
"Hehehe, this time my plan won't fail to make that Keyboy into one of my Underworld residents, MWAHAHAHAHA." Hades laughed maniacally, making the flames on his head blazed fiery.
Inside the lobby, the four were making their way onto their quarters, however something was in Kairi's mind as she asked "So, Sora, can you tell to us?"
"Huh? About what Kairi?" Sora asked, not having any idea about what the red haired girl asked about.
"Of course why did you pick the last one, silly." Riku answered with mocking tone to Sora.
"Hey! I couldn't choose anymore, besides I like the unknown opponent in matches." Sora replied Riku upset.
"Why don't we rest up for now, so we will have enough energy for tomorrow's match." suggested Aqua as well as breaking the argument between Sora and Riku.
"You're right, come on let's go the quarters." Sora agreed as he walked inside his quarter.
After that the rest went to their quarters and decided to take a rest for tomorrow's match. However Sora didn't realize that the last match that he choose would be the deadliest match ever for once again in his life. Didn't want to be bothered by that, Sora let his mind passed and slept like everything bad would never happen to him or the others.
I think that's all for the first chapter, quite short.