Sonic Twilight.

Author's Note: Hello again, and welcome to my first Sonic and Kingdom Hearts crossover, despite that both franchises have joined together in my other stories in the past, such as my ongoing Sailor Moon Continuum fanfic franchise. This is done by the request of a friend of fanfiction and fellow author Haxorus knight, and is set after the events of Kingdom Hearts 3 as well as the alternate ending of my fanfic "Sonic and the Power of the Wisps".

So, here we go!

I don't own Sonic the Hedgehog. All rights belong to Sega. I only own the OCs.

Prologue: "Goodbye..."

Sora's Reality: Set during and after the events of Kingdom Hearts 3 and KH3: Remind...

"My whole journey began the day I lost her. And every time I find her...

she slips away again. I thought we'd finally be together. But she's out there, alone. Not for one more second."

"Sora, listen. The power of waking isn't to go chase hearts around!
Even if you do locate Kairi, you might never come home to us again."

"I will. And we'll both be back before you know it."

"Even with the power of waking, you can't just bring someone back."

"Hey, I've already restored six hearts. What's one more?"

"But that's not how it's supposed to work at all. The power of waking is meant to be used to wake and restore sleeping hearts, not to restore them after they've completely faded away from existence. You've done that six times before, and as a result, you've managed to greatly alter the course of history itself."

"You've broken a nature taboo."

"Nature..."

"A forbidden act. Break a taboo of nature, and you'll end up paying an extraordinary price...You'll lose your powers. You won't be able to use the power of waking...But that's not all. You yourself...will vanish from this world. And without your powers, you can't return to the world you came from."

"I don't care...There's a lot I don't understand, but I know that this is all I can do right now. I have to do everything I can to get Kairi back.
That's the whole reason behind my journey."

"...I can't stop you, can I?"

"Nope, I have to follow my heart."

"Hmm... Well, then this really is goodbye, so listen carefully to me...
You'll return to the past again, but you won't be able to rewrite it this time. No matter what happens, you have to accept it and move on."

"...Kairi!"

"Sora!"

At long last, they were finally together again. Sora held Kairi as tightly as possible as she did the same, tears forming in their eyes as for a while there both in the back of their minds, they thought they would never see each other again.

Then...

The moment came after the final battles...

"Kairi. Come on. Everyone's waiting."

"Chirithy, we're heading home. You should come with us."

"Whaaaat!?"

"Take it from me, it's not enough to wait for someone you care about. It's true that hearts are connected wherever you are. If it's impossible to be together, then all you can do is wait...But, if it is possible to be together, then that's how it should be...You know, this really is a beautiful place. But you'd enjoy it so much more with someone you care about. Before, when I was looking around with Kairi, I remembered how important it is...to share moments with friends...That's why you're coming with us. I'm taking you to see your friend, Chirithy."

It had been fun, being with Kairi and spending his final moments together while secretly watching over all of his friends as they celebrated in their own ways, reuniting Chirithy with his friend who happened to be, to Sora and Kairi's surprise, Ventus, and finally freeing Namine's heart from Kairi's as the now former Nobody's new body was completed in Radiant Garden. But as they had finally returned home to Destiny Islands where all of their friends including Namine, Riku, King Mickey, Donald, Goofy, even Hayner, Pence and Olette, and their now new friends, Axel, Roxas, Xion, Ventus, Aqua, Terra, and even the restored Isa, all played on the beach.

But as the fifteen year old Keyblade wielder sat on his favorite Paopu Tree with Kairi beside him, hand in hand, he knew that his time was up, and he had to say one final thing.

"Kairi...No matter where I go, I'll always be with you." Sora whispered with a warm smile, even though his heart ached, and not just because he was fading away from existence, but also that he would never see her or any of his friends again. But it didn't matter. As long as they were all safe, happy despite him being gone, and all of the worlds were finally free from Xehanort's evil grasp, he was glad.

"Sora..." Kairi whispered, a tear sliding down her face, trying not to cry as she felt guilt swell up in her heart. But before she could protest and claim that it was her fault, the final words he spoke made her stop.

"...I'm sorry for not saying this sooner, and I wish I had, but I guess...now is better than nothing." The spiky-haired teen added, blushing a little even as tears stung his eyes. "...I love you."

The auburn haired girl smiled back, responding. "Sora...I love you, too."

Sora felt his heart swell with so many emotions, as he nodded as he began to become translucent. "...Goodbye."

And with that, as the sun began to set, he blurred before fading away like dust into the winds and vanished without a trace. Just like that, he was gone.

Never to be seen again.

Kairi choked a sob, lowering her head as she began to cry. It wasn't fair! Why did Sora have to die for her? She was vaguely aware that the rest of her friends let out horrified gasps to see Sora, the young hero who had risked everything to make it all possible to achieve their victory, to bring back the fifteen year old princess of heart, gone just like that, which proved Mickey and Chirithy's dire warning. Yet Sora chose to ignore them.

As a result, he nobly sacrificed himself. He was the price to pay for winning the long war against Xehanort and the darkness.

Sonic's Reality: Set during and after the events of "Sonic and the Power of the Wisps-Alternate Ending"...

"You are not the cause for what's happened two months ago, Sonic. You're not the cause of what's happening now. You just got caught in the wrong place at the wrong time back then, but you managed to still save the world like you always do. I'm your friend, Sonic. I'd...never forgive myself if anything happened to you."

"Sonic, it wasn't your fault. You know that Eggman likes to mess with everybody's heads, and I think we can both agree that what he's trying to do now is messing with our heads to the next level. You know that I've always got your back."

"It's not your fault. You're just taking the blame over something that Eggman has done. What you did was only because Eggman had planned it for months without everybody knowing, and you had been caught off-guard. You didn't do anything wrong at all. Like how none of us knew about this place either, and I won't let you blame yourself for that creep's evil schemes, Sonic the Hedgehog."

"What makes you think we wouldn't want to do the same thing you've always done for us?"

We wanna be there for you and cheer you up too, Mr. Sonic. We're your friends."

"Yeah. I told you before, big bro. You should let us comfort you once and while."

"I ended the inner conflicted by heeding Maria's advice, because she was my support. The two have manifested by my emotions by thinking of the life I have now, that I am in control of my own destiny and mind. Like a dream or a nightmare that are mine alone."

"You're just a manifestation of all of my feelings of hurt I've kept bottled up inside me for way too long. My guilt, my fears, my sorrow, and my anger. The latter part mostly at Eggman, but some of it, along with the rest of what I felt and couldn't face more aimed at myself."

"You're everything that I couldn't forget, but I couldn't find within myself to face them 'cause I was scared. I was frightened with what I did, even if it wasn't my fault, but I felt solely responsible 'cause I wasn't careful enough. I was reckless, but I didn't have a choice. I had to find a way to face that fathead."

"I couldn't forgive myself, since I was afraid what other people would think. Even now I'm still worried. It was also because I miss Chip so much that it added to my sadness. But you know...I'm not alone, 'cause I got my friends who understand more than even I did. Even friends I'll never see again, everybody's always with me, even when we're far apart on the outside. Not only that, I never realized it completely, or that I'd forgotten about it."

"Maybe you're right about the being alone part, but you're wrong about my friends. Just like my freedom, my love to run, and my home, they mean everything to me. I love them with all my heart. We're family. Even when the world was split apart, and I was so devastated by it, and even when Chip, Sun and I worked hard to restore it back to the way it was, it only made me love Mobius and everybody even more."

"WHAT? WHY DO YOU SAY THAT?"

"Because seeing the world, places I've never been to, and putting it back together, and seeing it restored to normal made me understand just how important it truly is. It's our home, and no one should take it for granted."

Everything Sonic has learned and did, he had finally conquered his worst feelings of negativity such as guilt, anger, sadness and hate. With that, he had defeated the hallucination of the Werehog, and his resolve and confidence has finally returned, allowing him to save the Wisps and despite almost losing Yacker forever who had sacrificed himself, the Chaos Emeralds, hearing the fifteen year old hedgehog's pleads, granted his wish to revive the pure-heartened little alien.

It also allowed Sonic to save the Mother Wisp, who had knocked down Dr. Eggman back to Mobius along with his robots, destroying his Interstellar Amusement Park. With that, despite losing his power after restoring the giant Wisp, the hero of Mobius had been saved when the Mother Wisp, remorseful for her uncontrolled actions, saved his life and along with the other Wisps, returned him home to his planet, reuniting with Tails and the others and stopping the void.

Then came the moment of goodbyes as the Wisps would now be returning home.

"Hey, could ya' tell your Mom that I said thank you again to her for me?" The blue hedgehog asked Yacker, who nodded and no one needed the translator to say that he will tell his mother. The cute alien held a very emotional look as even he knew that the time has come to part ways. Sonic smiled emotionally and held up his hands warmly, and Yacker immediately flew into his arms for a final embrace. Tails joined in as the three friends shared their last group hug with tears leaking in their eyes, and the other Mobians held different reactions but all smiled none the less. Amy and Cream both looked ready to cry, Rouge wiped away a tear, Knuckles sighed and tried not to shed a tear, even Shadow's expression softened.

"We'll miss you, buddy. But we'll always be friends. Remember that." Sonic whispered to the curl-headed Wisp.

"Don't forget about us, okay?" Tails added, sniffling.

They stayed like this until the trio reluctantly let go with emotional smiles, before Wisp then held up his arm, and while everyone else looked confused, Sonic knew what this mean and cheered with a wide smile.

"Right on!" He cheered and jumped into the air, happily giving Yacker a high-five, and Tails, seeing this did the same with the cute alien who giggled. Everyone else smiled happily(except Shadow who simply smirked, Rouge who folded her arms with a smile, and Omega who stood there) before the two young heroes landed on the ground and the Wisp flew around them squealing, shaking hands with Cheese who beamed happily, and they each gave their goodbyes to the little aliens.

"You take care, Yacker." The blue hedgehog told his alien friend with a smile. "Make sure you and Mom don't get separated again, 'kay?"

Yacker nodded and with a single tear formed in his eye, waved a goodbye for the final time to Sonic and Tails, and to their friends before he flew back up to reunite with his mother and family. The Mobians back in their world watched as the Wisps, including the Mother Wisp who waved a goodbye to the young heroes who have saved them all, flew back to their home planet before they all used their powers to not just magically transport Planet Wisp back to where it came from, but also Sweet Mountain, Starlight Carnival, Aquarium Park and Asteroid Coaster back to their places and galaxies in the Universe, vanishing from sight.

Sonic and his friends, while saddened to see the aliens off, all smiled in relief and happiness as peace as finally been restored. Not just to the five planets that have gone through so much, but their own as well. The blue hedgehog gazed at the sky with a content expression on his face, before blinking in confusion as something caught his eye. For a split second, he saw the familiar pixie-thing, faintly floating who gave him a wave and a smile before vanishing from sight, to which he realized for the final time.

Sonic was surprised to have seen what he thought was a hallucination of Chip, but then smiled as he knew, right there and then, that he was finally healed from within. While he still had to fight Eggman again in the near future, he will get stronger and better to avoid in his enemy being stronger than him. All in all, the blue hedgehog conquered his own fears and doubt from the last two months. He, with the help of his friends, saved the Universe from devastation. Yacker was finally reunited with his mother, and had returned home.

'Thank you, Chip. Even though you weren't really there, you guided me along with my friends. And Yacker...I'll never forget you. I'll always be with you, reaching out for the stars.' Sonic thought to himself as he smiled warmly, feeling true peace and a new sense of freedom.

"Sonic. Are you okay?" Tails asked, tugging the cuff of his best friend's glove as he and the others noticed the blue hedgehog's silence.

"Yeah, I'm fine." Sonic replied, smiling down at his little brother. "Guess I was...speaking with my heart."

His friends all looked confused by this statement, but all smiled as the blue hedgehog chuckled, giving them a thumbs up and a wink. He had a lot to tell them, and he really couldn't wait to share his and Tails' story of their adventure before Sonic and everyone else returned their gaze to the sky, as the day was slowly coming to an end.

With a new one on the horizon, for a brighter day.

In the Prison of Evil-Set during the events of "Sonic's Space-Time Adventure" in an alternate reality...

The Prison of Evil, the place where no evil that were too unworthy to even become trapped in the Underworld and it's many counterparts in different dimensions, and could not pass on to the Afterlife and it's counterparts in the same way, the world of mostly a wasteland, and a dark city that was the home of dangerous creatures, and a prison within this world of a prison held many evil criminals that were captured and locked up and sentenced to death by the Executioner. Yet like all realities, there was more than just one.

This one is where Domain and the Time Eater cannot escape and thus are destroyed by the original version of Sonic the Hedgehog who along with his younger, alternate-self, are fighting and defeating at this very moment, watched by mysterious dark-hooded creatures known as the Octosaurs, who, unlike most, can view their alternate reality go through these events, yet there were still people in their own that needed to be saved.

"The Chosen One will succeed. Soon everything will be alright in all realities." Spoke one Octosaur, who went by the name of Soloman, the High Guard. Within him is the King of all Octosaurs, who sat in his throne.

"Indeed. Yet, in our reality which links to that of Sonic's other self who remains fighting against Dr. Eggman, in that world, it is about to face another crisis which must be solved very soon." The King spoke grimly, lowering his head.

Humming in thought with concern, Soloman turned to his ruler and questioned carefully. "Is it true that one of the other Multi-Reality world's have inadvertently connected to ours by a human child who was not thought as a powerful weapon's chosen one?"

"Yes. A boy who was ordinary on the outside, yet deep within, his heart, much like the blue child's, is pure yet fragile. His spirit matches that with Sonic the Hedgehog. But for the love of those he cherishes and for his reality, he changed history when it was forbidden. He has broken the ancient taboo, and the price is for that he must leave his home to enter a reality where he can survive. But to get back, it is impossible, even if the people he loves find a way to get him home." Explained the King.

"Should they find their way to that reality, they would become trapped themselves. Is there anyway to have the boy return to his reality?" Soloman asked.

"There is only one way, and if we are correct, the fate of our reality as well as the boy's lie in the hands of only one in this world, who like the one saving all realities of our Multi-Reality, is a pure hero who must do what it takes as he is the chosen one. The others, including the child, must remain unaware because of their battle against the two destroyers of Time."

The High-Guard's eyes rose in shock as he immediately knew who the King was talking about. "Sonic the Hedgehog...of our reality."

"Like for our alternate selves, the time has come for the blue child to arrive here to rescue those innocent people...he is the only one to help the child...the bearer of the Keyblade." The King nodded. "We must keep an eye on them, and you, Soloman, will enter Sonic's world to secretly guide them."

While he felt a bit uncomfortable to enter the world outside of the Prison of Evil as it wasn't possible even for the Octosaurs as only heroes like Sonic can enter and leave at will as long as their hearts stay true, Soloman knew there was no other choice. So he bowed and responded obediently. "Yes, sire."

Things were about to become dangerous once again. Though not as much as the Time Eater or Domain, but it was close enough. Because Sonic was the only one to set things right in every reality as almost every version of him is a hero.

Presenting...

An Sonic the Hedgehog and Kingdom Hearts Crossover...

SONIC TWILIGHT.

A/N: I'm not sure how this story will turn out, but I will do my best with it as well as try and finish my other stories as well. I hope this prologue is alright and as mentioned, this story is set in an alternate universe where Eggman still lives, but he, along with Sonic, are unaware of the events that are happening in my main head-canon Sonic universe.

See you later!