A/N: Well, here we go again. I've always been interested in Time Travel Luffy stories, being a fan of Once Again in particular myself, so I wanted to take a crack at it myself. Just with a couple of twists here and there.

This story is, if you've guessed already, inspired by Re:Zero, at least in some form. There will be no pairings for a while, as this is a slow burn. Plus Luffy's like, physically five at this point in the story.

Summary:

After suffering a crippling defeat at the hands of Kaido, Luffy is sent back to his seven-year-old self for a chance to fix things. But meddling with timelines is a dangerous thing, and can have dire consequences. Re:Zero AU, in which Luffy's interference with his own past and others results in domino effects he could never even imagine.

The first thing Luffy noticed was the blood - or lack thereof.

When he had held Ace in his arms during his brother's final moments, there was plenty of that. Of course there was, having a fist driven through your stomach would cause a large amount of spillage for anyone, even for a man made of fire. It was strange, then, to see their remains on the floor, what little remained of them, not bleeding.

He vaguely remembered Chopper - poor, sweet, innocent Chopper - telling him about the effects of cauterizing the wound after he had asked. The doctor had been so ecstatic to explain something to him, and Luffy himself was just as excited to listen to the lesson, and now his body was nowhere to be found - only his hat remained.

Of course, Kaido must have eviscerated him. His body was small, after all.

Luffy dragged himself across the dirt with his remaining arm, the other one having been destroyed in the blast, and settled by his doctor's hat. A moment of silence washes over him as he picks it up, choking back tears.

It smelt of cherry blossoms and ash.

Ever since Marineford, he always had an aversion to burning flesh. That was nothing new to him, not after his brother's body was laying on top of him, smoke rising from him, and the wretched scent of burnt flesh filling his nostrils and breath, to the point where it was hard to breath and he would have only gagged if he wasn't crying -

He froze up, coughing up a fit. Even now he found it hard to think about Ace's death, and it was only making his mental state worse. Shaking violently, he placed Chopper's hat down, standing up with trembling knees.

"Brook…" he started, bottom lip quivering. "Brook, are you out there?"

He was half-expecting Brook to jump out from the ash and yell something about a skull joke, but nothing happened. All that remained was silence.

"Come - come on," Luffy laughed. "It's been a nice prank, but it's over now. Right guys?"

Dead silence.

"Franky? Robin?" There was no way that blast could have hit Franky - he's a cyborg, after all. And Robin always had a trick up her sleeve. She would've found a way to get out of the way in time.

His darting eyes paused on their bodies. Half-gone. Even some of their faces were missing.

Luffy didn't scream. Not yet. There was still a chance that some of them survived. They weren't so weak as to die from one measly attack from Kaido, after all. The Straw Hat Pirates were survivors, they were fighters, they were winners. They were meant to explore the rest of the oceans together. They couldn't die here. They just couldn't.

On the other side of the rubble, he spotted familiar mint-green hair through ash and dust, twitching ever-so-slightly. There was a moment of silence, where Luffy didn't dare allow himself to hope, before a faint cough reached his ears and Zoro moved. As soon as he showed the first signs of life, Luffy rushed over to his first mate with his heart racing in his chest. The swordsman groaned.

"Oi, Zoro!" the captain forced a relieved smile. "I'm so glad you're - "

He froze. In a moment of horrified realisation, he finally caught sight of Zoro's condition.

Both of his legs were missing, as well as a large chunk of his stomach. Again there was no blood. The wound was burnt over by the fire blast. Zoro spat blood on the ground, lifting himself up with his arms, before a tremor shook through his whole body and he fell to the ground again

Luffy screamed.

Every one of them, every last one - Brook, Chopper, Franky, Robin, Zoro, Usopp, Sanji, Nami, Law, Kidd - they were all annihilated by Kaido. Just one shot was enough to wipe them all out. It was unfair, it was sickening, it was not what their journey was supposed to be. It wasn't supposed to end here. His voice turning hoarse, he collapsed to his knees, eyes rolled back in his head. Somewhere above him he heard the booming voice of Kaido, no doubt taunting him for his failure.

Numbly, he registered King cuffing his legs and remaining arm with seastone. The twisted bastard - Luffy had only heard rumours of what he had done to Killer, and he had witnessed the aftereffects of it. But whatever was in store for him couldn't be any worse than the pain he had just been through, the humiliating and torturous feeling of losing his entire crew. Just like Sabaody, all over again - he was too weak to save any of them.

His mind went blank.

He barely registered King carrying him off somewhere, and he didn't notice when he was shackled to a wall. Even the searing pain of a burning rod prodding into his skin wasn't enough to wake him up from his near comatose-like state. It must have been hours of whipping and branding and torture, but to him it felt only like a fleeting moment passing in time. Finally, he feels a prick on the back of his neck - injection, he thought.

"This is a prototype," King said. Luffy didn't have the strength to glare at him. "A defunct Smile for Devil Fruit users. Caesar didn't say whether it was ready or not when he sent it. But congratulations… you're the first."

Luffy laughed.

And then he died.

Dying wasn't as peaceful as he'd thought it would be. Contrary to what he believed, it was not a gentle passing, but rather like he was violently drowning, gasping for air that would never come. Luffy reached with his hands out to the sun, praying for a way to return, to find his comrades again and start anew - and this time defeat Kaido.

He was in a dark place, full of shadows and whispers and mist. It's haunting, to him, as if he can feel every last friend of his who died blaming him for his failures.

It takes him a while in his panicked state to realise that both his hands had returned - he was somehow healed. What's more, they were a lot smaller than he remembered them being.

Luffy tried to scream, but all would come out was a hoarse laugh.

It must have been a result of the Smile injected into him. Luffy was no stranger to laughing, or joy, but the forced grin upon him did nothing but anger him. He pulled at his lips, begging them to go down, but they never would. Instead of stretching down normally, Luffy felt a pain drive through his cheeks, and let go promptly. There was a similar effect when he'd don the seastone cuffs. He'd lost his Devil Fruit powers, too.

Collapsing to his knees, Luffy punched the ground and choked back tears.

"D-damn - shishishi - it!" he squeaked. He froze, the blood draining from his head.

That was not the voice of a grown man. That was the voice of a child.

"What the hell?" he said, his voice still somehow high-pitched. "What - what's going on here?"

Slowly around him, things came into view, as if materialising out of nowhere. Floorboards, a bed, a drawer, a door, a mirror, a window. Outside it looked like it was still coming into place, with dark clouds looming over him. He was clearly in a room of some kind, one that tugged some sort of familiarity deep within him that he didn't know how to explain.

The mirror. He had to see the mirror, see what damages were caused by King's doing - and see why his hands were so damn small.

Luffy looked in the mirror and laughed. A child laughed back at him.

This must be it. He must finally have gone insane. After the loss of his whole crew, this is what he has become. A laughing shell of his former self, seeing things that weren't there. The first conclusion he had wasn't the most logical, but it was the only idea he had.

"Alright, Bonney, that's enough," he said. "You can turn me back now."

No answer came.

He'll admit, he didn't get to know her very well in Saboady, just that they had an eating competition together that ended in a draw. That apparently was enough to garner each other's respect as rivals. What he did know of her was the fact that she could alter people's ages.

Yes, that's right. She must have rescued him from Kaido somehow, and was playing a prank now.

He smiled. "It's not a very funny joke, Bonney."

Still, the only answer he received was silence. Luffy frowned and looked over his shoulder at the door, as if expecting it to open any second. When it didn't he walked towards it himself, holding his arm up to twist the doorknob to no luck. The door wouldn't budge.

"Bonney?"

Turning back he stared at himself in the mirror again.

He was a child.

He was a child again.

This wasn't Bonney's fruit power, this was something else entirely. As soon as that realisation hit that there might be no fix for this, Luffy fell on his backside, still staring wide-eye into the mirror, a grin etched on his lips.

That smile. That stupid smile. He hated it, he wanted it to stop - he didn't want to smile anymore, not when he had lost so much.

Screaming loudly, his cries mixed in with hysterical laughter, Luffy pulled his arm back and swung at the mirror. Shards of glass shattered to the floor with a resounding smash, with some of the unlucky shards sticking into his hand, making him bleed. Luffy could only laugh in response as the cold pain seared through his skin. He was no stranger to getting stabbed, but somehow his pain tolerance had lessened. Clutching his hand to his chest, he continued to cry out in mental and physical pain, somehow getting in hagged breaths of laughter between his screams.

He pulled himself to a corner and hid there, not noticing the dark clouds disappearing from the outside view, or the booming footsteps rapidly approaching. What he did notice, however, was the door suddenly swinging open, and the sight of his grandfather standing in the frame - albeit looking much younger than Luffy last remembered.

"Luffy! I know you're sad to see me go, but don't make a ruckus - Luffy?" Garp paused, eyes darting to the broken mirror to the shards of glass on the floor, and then to his grandson's injured hand. His bushy brows furrowed in worry. "Luffy, what happened here?"

But Luffy was silent. He could only stare at his grandfather, dumbfounded - at least, as dumbfounded as one who was injected with a Smile could be.

"G-gramps?" Luffy whimpered. "Ah… ahahaha… Why are you here?"

Now Garp was not a model grandparent. This was clear to anyone who saw him. He was rough on his grandkid, he was stubborn, and he refused to listen to reason. There was a desire within him to see his descendants follow the righteous path of the marines, to not go down the dangerous path his son did. But when something was off, Garp knew there was something wrong. And there was absolutely something wrong with Luffy.

Crouching down to be eye-level with Luffy, Garp held out his hand. Hesitant, Luffy stuck out his own injured hand, resting it on Garp's. He sniffed and grinned.

"I want you to be honest with me," Garp started. "Are you trying to look tough?"

Luffy hiccuped. "No, no!" he said. "I'm - I'm just confused!"

It was honestly true. He didn't have the faintest clue what was going on - he was often called too dumb to figure out the most simple of things. Most times he would wave it off and call it a mystery, but this time he had to know.

"Gramps?"

Garp raised a brow. "Yes?"

"Am I in hell?" It was the only natural explanation, of course. There was no way he could have survived Kaido's attack and King's torture, and he knew Garp wasn't going to heaven. So hell it was.

"...Luffy, did you hit your head again?"

"No!" Luffy shot back. "I just don't understand how - how - " He bowed his head down. "I don't get it gramps."

Drops of water fall onto his injured hand and his shorts. It takes him a moment to realise he's crying, and so it does for Garp to. But even then, his smile never leaves his face.

Garp frowned. "Luffy, can you stop smiling?"

Luffy shook his head.

"Who did this to you?"

If he had the energy to glare, he would. Even his tears had turned to angry blotches. Kaido. Kaido Kaido Kaido.

"It was K-"

The words froze in his throat, refusing to come out no matter how hard he tried. He began to breathe with shallow breaths, his pace quickening and his heart pounding against his ribcage. Perspiration ran down his neck and face, as he quickly began to find it hard to breath.

"S-shit! Luffy!" His grandpa was violently shaking him in worry. "You gotta breath, Luffy!"

But he couldn't, no matter how hard he tried. It was like a hand was grasping at his heart, stopping it cold. No matter how hard he tried, he couldn't say Kaido's name. Damn it, this was pissing him off!

There was a moment of silence, when Garp stopped shaking (thinking that maybe that wasn't the brightest idea) and Luffy collected his thoughts, when he could finally breath again. The hand had disappeared from his heart. Garp quickly settled Luffy down on the bed and sat down next to him, worry etched on his features as he waited for Luffy to continue.

"...I - I don't know," Luffy lied, voice trembling. "I forgot."

He felt something warm and large on the top of his head, and it takes him a moment to realise his grandpa is ruffling his hair. Looking up with awe, he's greeted with a wide grin. "Don't you worry, Luffy! We'll work out who did this and fix you up in no time." Garp raised his fist and punched his own palm. "I'm gonna teach them a lesson - don't mess with Monkeys!"

Luffy wondered if Garp could hold his own against Kaido. Surely he could - the hero of marines, who fought against Roger himself, could hold up against Kaido. But for how long? How long would Garp last until he too would inevitably fall against the fearsome might of an Emperor?

This did nothing to lift his mood.

"Ah - you're still injured!" Garp exclaimed. Luffy stared at his hand numbly. "Come on, let's get you patched up. We'll visit Makino!"

Luffy glanced up at his grandfather. "Makino? She's here too?"

"Why wouldn't she be?" The older man picked Luffy up and held him gently, careful not to hurt the injured hand any more. "You're still in Foosha Village, you know. No matter how many times you try to stowaway on my ship, you'll remain here."

Foosha Village.

The name swept through him in shock. He hadn't heard about his home town in years, not since he left almost three years ago. Back then, he'd been a lanky teenager. Now he was… a wimpy child.

Now, Luffy was not smart. But sometimes - sometimes - he could make brilliant deductions.

This was one of those times. For as his grandpa walked with him, himself grinning ear to ear, towards the young and beautiful bartender, Luffy had only one thought in his head.

I've gone back in time.

So, what did y'all think? I'd love to hear your thoughts in a review!