The city lay in ruins from the destruction wrought by Dr. Eggman. With the massive power of the Death Egg Robot sentinels, there would be no taking it back...not without an extremely coordinated effort, that is. Of course, the city's inhabitants had long given up on living under the destruction of the doctor's rule, let alone resisting it. Now a coordinated resistance group fought to bring an end to Eggman's rule.

This was where his fall would begin. Or so they hoped.

It was under these circumstances that a mysterious wormhole appeared in the middle of the city. If someone had been nearby, they would have heard a faint screaming from inside the wormhole. The scream got louder and louder until finally a boy fell out of the hole, landing on his back. A little yellow creature was cradled in his arms: a Pikachu, to be exact. The boy shuddered a moment, regaining his senses, before opening his brown eyes.

"Are you okay, Pikachu?" he asked his friend.

"Pi...ka," Pikachu nodded with a smile.

"Good," he smiled. He sat up slowly, wincing at the pain in his back. His name was Ash Ketchum, a new trainer from Pallet Town who had gone on an extraordinary journey. "Ugh," he moaned. "That was a nasty fall. Do you have anymore first aid supplies, Sorrel?" He waited a moment, expecting a response, but none came. "Sorrel?" He looked around, only to discover that he and Pikachu were alone. "Verity? Sorrel?! Guys?! Where are you?!" There was no response. "Oh no," he said, crestfallen as he realized what had happened. "That wormhole must have taken me away from them!"

"Pikachu?" Pikachu asked sadly.

"Looks like we're on our own again, buddy," he said, shaking his head. Then he looked up with determination once again. "I don't know where our friends are, but we'll find them again. I promise!"

"Pika pika!" Pikachu agreed, jumping up on his shoulder.

Ash chuckled, glad to have at least his best friend with him. Then he looked up with a curious expression. "Now where exactly are we?" As he looked around, he finally began to take in all of his surroundings. "What in the world happened here? This place is completely destroyed!"

"Pikachu," Pikachu squeaked softly.

At that moment, a loud crushing of metal erupted behind them as a shadow fell over them. They whirled around to see a massive hunk of metal behind them. It was attached to a massive robot that was glaring down at them with a sinister red eye.

Ash didn't even hesitate. He just turned tail and ran. The robot began firing at him, its shots narrowly missing him each time, though they all made him jump. His legs pumped fast enough to power an electric generator, but it wasn't enough to escape the giant robot. Finally, his foot caught on a crooked metal rail on the ground, tripping him. He fell face-first onto the ground, and Pikachu flew off his shoulder. Ash quickly regained his bearings and looked up, seeing Pikachu on the ground. He heard a mechanical whiz and looked up, seeing the robot was aiming at…

"PIKACHU!" he screamed, running forward and hugging Pikachu tight. The robot fired its blast, and Ash braced himself for the burning feeling that would follow.

It never came.

Instead, he heard what sounded like water putting out a fire. And while the heat of the blast was still close by, he and Pikachu remained unharmed. He was confused and looked up to see a strange, blue creature blocking the blast with what appeared to be a shuriken made of water.

"Whoa!" he exclaimed. "What Pokemon is that?!"

The Pokemon slashed through the the blast, ending it, before launching the shuriken directly at the robot's eye. The robot, damaged by the attack, decided to fall back for the time being to recover itself. The Pokemon then turned to Ash with a puzzled expression.

"Nin?" it said.

Ash blinked, unsure of how to respond. "Uh…" he said, "thanks for saving my life. I –"

"Greninja!"

It was the voice of another person, which Ash confirmed as someone ran up to the Pokemon that saved him. This person seemed similar to him, as he had similar messy black hair and brown eyes. However, he looked older.

"Whew!" he said as he came up to the Pokemon. "That was close. A second too late and that robot would have finished these guys off."

"Ja, Greninja," Greninja replied, pointing to Ash.

"Right," the other trainer nodded, turning to Ash. "Are you all ri–WHAT THE –?!"

Ash blinked in confusion at his companion's bewildered face. "What?" he said. "Never seen a guy with a Pikachu before?"

The other trainer stared in shock. "Um...who are you?" he asked.

"I'm Ash Ketchum, a new trainer from Pallet Town," Ash replied. "I'm a little lost, though: my friends and I were just winding down after our adventure when –"

"How did you get here?" the other trainer interrupted, still in shock.

"I got sucked into some wormhole or something," Ash replied. "Any idea where we are?"

The other trainer began to recover from his shock and started thinking about what was happening. This must be my past self! he thought. He must have come to the future the same way Sonic's past self did!

"Who are you, anyway?" Ash asked.

Fully recovering from his shock, the other trainer cleared his throat and started to speak again. "I don't exactly know how to answer that," he replied. "If you want to know where you are and who I am, then you'll have to be prepared for something really crazy."

"Sure," Ash shrugged. "I've seen a lot already. What's a little craziness stacked against –?"

"I'm Ash Ketchum from Pallet Town."

Ash stopped mid-sentence, his face freezing. All he did was blink for two seconds before processing what he just heard. "I'm sorry, what did you just say?"

"You heard me right," the other Ash replied. "You and I are the same person. I don't know how or why, but you must have travelled to the future somehow."

"What?!" the first Ash exclaimed in shock. "Okay, THAT'S just too crazy to believe!"

"I did warn you, didn't I?" the other Ash said. "I know it sounds crazy, but it has to be true."

"No!" the first Ash snapped back. "Getting to meet the legendary Ho-Oh is one thing, but time travel?! That's impossible! What makes you think that's what's happening here?!"

"Because a friend of mine recently went through the same thing," the other Ash explained. His expression became more urgent. "Listen, we need to get out of here. It's too dangerous."

"No way!" the first Ash shouted. "You're lying! You must have brought me here so you could kill me!"

"Calm down," the other Ash said, raising his voice slightly but keeping his cool. "I know it sounds crazy, but you have to believe me."

"Why should I believe you?!" the first Ash screamed. "I don't even know you! You're a liar, and I'll prove it by defeating you in battle!"

The other Ash, seeing his past self wasn't willing to cooperate, clenched his fist in disappointment. "Fine," he said. "If a battle's the only way to convince you of the truth, then I'll battle you. If you win, I'll leave. But if I win, you're coming with me."

"Fine," the past Ash retorted. "But I won't lose." He pulled out a Pokeball. "I'll show you the power my Pokemon has gained on our journey. Charizard, I choose you!" He chucked the ball, unleashing the massive dragon-like Pokemon.

"Zarrrrrrrrrrr!" it roared. At this, the present Ash smirked.

"Seems my past self hasn't learned that it take more than power to win," he said to himself. "That's no excuse to go easy, though. Disobedient or not, Charizard's a powerful Pokemon. Greninja, let's show our friend here what we're made of!"

"Ninja!" Greninja nodded, stepping forward.

"Your move, Ash," the present Ash said.

"You'll regret that!" the past Ash sneered. "Charizard, use Flamethrower!" Charizard obeyed, firing a jet of flames at Greninja. The nimble ninja Pokemon leapt into the air to dodge the attack and threw a Water Shuriken at Charizard, striking it. "Slash!" the past Ash commanded. Charizard flew forward, claws glowing, and slicing through Greninja's torso. Greninja cried in pain, clutching its torso.

"That Slash attack hurt," the present Ash said, concerned. "We need to finish him quick if we want to win. Greninja, use Night Slash!"

Greninja shot forward as mysterious dark energy formed in its hands, solidifying into dark energy blades. It flew forward and slashed through Charizard, who wasn't fast enough to dodge, causing significant damage. It then followed this up with another Water Shuriken, which inflicted even more damage on Charizard.

"Charizard, use Dragon Rage!"

"What?!" the present Ash exclaimed. Charizard raised its head as its eyes and tail flame glowed white. Energy formed in its mouth, and it fired at Greninja, who took the full force of the attack. Greninja flew backwards and landed on its back. For a moment, it laid there in pain.

"Way to go, Charizard!" the past Ash cheered.

"Zarr!" his Charizard nodded happily. At this, the present Ash's eyes widened.

"Charizard isn't just obeying his every command," he said to himself in shock, "he's doing it because of their bond. He's loyal to him! But didn't he say he was a new trainer from Pallet Town?! This didn't happen to me!" He clenched his fists and teeth as Greninja stood up to face his opponent. "It seems I underestimated you," the present Ash said. "But that's a mistake I won't make again!" At this, Greninja's eyes began to glow red. The past Ash watched in shock as a swirling column of water enveloped Greninja. The water quickly condensed onto the ninja Pokemon's back in what appeared to be a massive shuriken. The past Ash noticed that Greninja now looked different from before.

"What in the world did you just do?!" he cried.

"You'll understand when you're older," the present Ash replied. "Now to end this! Greninja, use Night Slash!"

"NinnnnnnJAAAAA!" Greninja screeched as it slashed through Charizard with a powerful dark energy blade.

"Charizard, use Flamethrower!" the past Ash commanded. Charizard obeyed, firing a torrent of flames at Greninja. Greninja, however, blocked it with a quick Water Shuriken, deflecting the fire away.

"Now, Greninja!" the present Ash cried. "Water Shuriken to finish this!"

Greninja grabbed the shuriken off its back and launched it at Charizard. The impact of the attack rocked Charizard. It struggled to stand after the attack, but it proved to be too much as it fell to the ground, defeated.

"Charizard!" the past Ash cried in shock. "Are you okay?"

"Rrrr," Charizard rumbled softly.

"Thanks for your hard work, Charizard," he said, recalling it to its ball. "You deserve a nice rest."

"Great work, Greninja," the present Ash said as his Pokemon reverted back to its normal form.

"Well done, both of you."

The sudden voice caught both of the trainers off guard. The past Ash looked up in confusion while the present Ash looked up in fear as a strange being enveloped in a red aura descended to them, ominously clapping for them.

"I see you brought your past self as reinforcement," the creature sneered at the present Ash. "How tragic it will be when both your past and your present end in one blow."

"What do you want?" the present Ash growled.

"What's going on here?" the past Ash wondered.

"What do you think I want?" the being growled at the present Ash. "You and your friends pose too large a threat to the doctor's reign. Plus you yourself are pretty annoying. I'll just eliminate you and your pathetic doppleganger and be done with it."

"Hey!" the past Ash shouted, prompting the being to turn to him. Now that they were face to face, Ash saw his frightening yellow eye. But he swallowed his fear and continued speaking. "I am not pathetic! I'm destined to be the world's greatest Pokemon Master! You can't defeat me!"

The being was unmoved by his speech. "Courage, it seems, likes to wear blue quite a bit," he sneered. "And yet...what's that I smell?"

"You think you can intimidate me?!" the past Ash growled.

"Ash, don't fight him!" the present Ash called. "You can't beat him!"

"Why should I be scared of you?!" the past Ash snapped, ignoring present Ash. "I don't know a thing about you; not even your name!"

"You may call me...Infinite," the creature replied, "in the brief moments that remain to you."

"Ash, trust me!" present Ash cried, getting desperate. "You can't win this one!"

"I'll show you our true power!" past Ash said to Infinite. "Pikachu! Let's take this creep down!"

"Pika pika!" Pikachu agreed, ready to battle.

"The little rat again," Infinite muttered. "Or perhaps this was before."

"Don't do it, Ash!" present Ash screamed.

"Pikachu, open this up with Quick Attack!"

"Ash, stop!"

Pikachu launched forward and...hit nothing. Confused, he looked to the side and saw Infinite standing there. "What?!" past Ash exclaimed. "But...he was just there a moment ago! Pikachu, Thunderbolt!" Pikachu unleashed his signature attack. Infinite deflected it, however, and jumped into the air, hovering as he launched an energy bolt at Pikachu. Pikachu dodged and tried to use Quick Attack again, but Infinite kicked him into the air and then followed up with another kick that sent the poor Pokemon crashing into a wall. "No!" past Ash cried.

"Your pet rat was weak," Infinite sneered at present Ash, who watched in horror. "I doubt your past self could even be considered a worthy opponent."

"Then let him be!" present Ash growled.

"Why should I?" Infinite replied. "If I kill him now, then I can eliminate you both in one fell swoop."

"Pikachu, Quick Attack again!" past Ash shouted. Pikachu tried, but only met with the same result as he got kicked into another wall. He fell to the ground and collapsed. Past Ash ran towards him, but Infinite stood in his way. He raised his arm, ready to strike.

"NO!" present Ash screamed, throwing several Pokeballs in desperation. Several powerful Pokemon leapt out of them: Charizard, Sceptile, Infernape, and Krookodile all joined Greninja in staring Infinite down.

On seeing this, Infinite lowered his arm and blinked in surprise. "Desperate, are you?" he asked. "You wouldn't truly risk that again. After all, you remember the damage it caused last time."

"I won't let you hurt them," present Ash snarled. "If I have to do it again to stop you, then I will."

Infinite huffed slowly as though breathing through a helmet. "Fine then," he said. "I'll put off killing you two for now. Best pray that you have similar luck next time we meet." With that, he floated into the sky and disappeared.

"Pikachu!" past Ash cried, coming up to his Pokemon. "Are you okay?"

"Pi...ka…" Pikachu replied weakly.

"Come on," present Ash said, recalling all his Pokemon. "I know a place we can go to heal your Pokemon."

"How far is it?" past Ash asked.

"Close enough to be safe," present Ash replied. With that, the trainer from two time periods ran through the ruined city to find safety.

This was inspired by the true ending to Sonic Mania, and that's all I'll say to avoid spoilers.

Spoilers aside, though, I've been thinking about a premise like this for quite some time now. After all, Sonic Forces already established that Sonic's past self came to the ruined present thanks to a strange new power that Eggman got his hands on, thereby allowing him to finally conquer the world. Naturally, in a Sonic-Pokemon headcanon, it would make sense for Ash to get similar treatment. And what does this year's Pokemon movie just so happen to be? A story of the beginning of an alternate Ash's journey! So the Ash of I Choose You comes to the Ash of the main series' dimension and joins the Resistance. Pretty cool, huh?

Man, I love the coincidences that happen between these two franchises!