This is a Challenge from Mellra. It's a rather loose challenge, simply asking for someone to write a story where Luffy is a saiyan, or has saiyan ancestry. I have communicated with him, and we're working together to form ideas for this, though I am the one doing the writing.

Rate T, but their may be some elements that stretch this rating, such as language. These are Pirates after all.

I will be attempting to update this on a Bi-Weekly schedule, but I don't promise anything. Life has a way of kicking in the back when your not paying attention after all.

Disclaimer: I do not own One Piece, Dragon Ball Z, or anything else that you may, or may not recognize. If you recognize, it's not mine, and it belongs to it's respective creator and/or owner.

~Prologue~

Garp sighed as he looked at his young grandson who sat eagerly in front of him, as well as his adopted grandson, Ace. It had been 2 years since Sabo had died, and, quite frankly, Garp was surprised it had taken until last night for Luffy to ever see the full moon.

He remembered the event very clearly. He should, as his memory wasn't that bad yet, and it had only happened the night before.

"Luffy you little shit, I told you to run! Run like the devil himself is upon you! You need to work up that stamina!" Garp shouted, but Luffy wasn't paying attention.

He looked at the boy a little more closely, and noted that his mouth was opened slightly. On top of that, he had an even more blank then normal look in his eyes. Actually, now that he thought about it, the boys sclera was slowly taking over his iris and pupil.

He knew what was happening, and he prepared himself for combat. But then, Luffy did the one thing he hadn't expected.

"I've never seen the moon like this before, gramps." Luffy told him. "I feel... powerful."

Then it happened. His grandsons eyes went completely white, before turning entirely red. He expanded rapidly, his rubber body no doubt making this transformation far less painful, perhaps even painless, then the legends said it would be.

Luffy had transformed into a giant ape. The legendary Oozaru.

"Gramps? Why are you so small?" Luffy asked, suddenly.

Garp opened his eyes, letting the memory fade again. The legends passed down from their ancient ancestor said the form was uncontrollable. But Luffy had controlled it perfectly. His guess was, the Oozaru form heightened a saiyans connection to their instincts, and Luffy relied so heavily on instinct to begin with that he hadn't even noticed a difference.

Ace had said the form fit Luffy, once he'd found out it was Luffy.

He didn't know just how right he was.

"Oy, old man, you said you'd explain to us now what happened to Luffy last night, right? He ate the Gum-Gum Fruit, not the Giant Ape fruit, so it ain't a Devil Fruit ability." Ace stated.

Garp nodded. "That's right. It's the mark of proof of our lineage. The lineage of those who bear the initial D in their name."

Ace frowned. "So... I'm the same?"

Garp frowned. "Not really. Gah, I'll start from the beginning so it makes more sense.

"See, long time ago, during the century the World Government wants to cover up, the Void Century, our mutual ancestor, the ancestor to all those who bear the initial D in their name, landed on our planet, Oceanus. He wasn't a native fishman, or an extremely late human arriva-"

"Wait, what do you mean late human?"

Garp scratched his head. "Uh, well, I dunno the specifics, but humans ain't native to this planet either. Only Fishmen, Giants, Minks, and Merfolk are. Well, of the sentient creatures I mean. Apparently the humans home planet was dying, so they fled. Scattered to the ends of the universe. From what little I know, this planet took two centuries before humans stopped struggling to move in their early years of life, and another century before they didn't even notice the extreme gravity on this planet for most of their lives. Apparently the gravity here is ten times their original planets gravity. Must have gotten really lucky none of the natives found them during that time frame, or there probably wouldn't even be any humans. Anyways, not the point.

"Point is, our mutual ancestor was a saiyan. He arrived claiming his own home planet was destroyed. Long story short, he bred with humans, and, in honour of him, his descendents are all given the initial D in their name. His name was Monkey Daiish. I know all this because I'm one of his direct descendants. One of the few who still bears his original last name, Monkey. He chose it because of the form he could take. The Oozaru. The Great Ape."

Luffy and Ace nodded, though whether Luffy was actually paying attention was another matter entirely.

Garp continued. "To be honest, I wasn't actually sure it was true, but Luffy proved it. I mean, he sort of proved it, being the first since Daiish himself to be born with a tail, but since it could have been a quirk of genetics, perhaps evolution, I didn't want to jump the gun. The transformation certainly makes me think it's true though. But, if it is true, then everything else might be true as well."

"Such as?" Ace asked.

"That saiyans like us, can begin really serious training at a young age. You brats thought you were going through hell before? You're going to be begging me to send you to hell by the time training is done!" Garp shouted, laughing at the end of his sentence.

Ace and Luffy winced, and turned to run, only to find themselves over Garp's shoulders, while he laughed like a lunatic.

~Four Years Later~

Luffy wasn't the brightest guy around. That was for sure. But after hearing all the different tales Garp knew about saiyans that were passed down in their family, Luffy had decided he liked being different from regular people.

Ace was different too, but not as different as Luffy. Luffy had proof he was a saiyan. His tail.

And with all the legends about how great an empire the saiyans had once had before their destruction a thousand years, or more, ago, he'd altered his dream. He wouldn't just become the Pirate King. He'd build a Pirate Empire.

That meant he'd need loyal followers though. People willing to help him. As many as he could gather. Empires were big after all.

"So, what do you think, Ace?" Luffy asked, having explained his plan to Ace. After all, he wasn't very bright. But Ace was pretty smart.

"Well, a Pirate Empire means your gonna need lots of followers. Thousands. You can't fit them all onto one crew. But you can't just start off gathering thousands of people. Think about from the Marines point of view. A powerful rookie pirate gets an armada, and takes the Grand Line by storm? They'd wipe your whole crew out just to prevent another Whitebeard or Kaido from popping up."

"So, I start small?"

"Not really small. Get a large single crew first, and make them powerful. A powerful crew on a single ship is much better to the Marines then a powerful crew spread out over a hundred ships. Plus, it'll be easier for you to slip past them and escape." Ace explained.

"Wow! You're so smart, Ace!"

Ace rolled his eyes. It wasn't smartness. It was common sense. Before Ace could answer however...

"zzz...ZZZ...zzz...ZZZ..."

Luffy grumbled. "Stupid narcoleptic brothers."

Instead of figuring out how many people he should recruit from Ace, by waking him up, he instead left to go train. He loved training. He started with his usual warm-up of running around Dawn Island, beating the crap out the Goa Kingdoms town guards, stealing an entire butcher shops supply of meat, carrying two massive boulders in his hands, and then climbing a cliff with just his tail and feet, while still carrying the boulders.

It was getting harder and harder to find enough to do in a single day to give himself the burn he wanted to feel, but, until his grandpa came back with the heavy weights he'd promised him on his next birthday, he was stuck.

So, after his basic warm-up, he went straight into straining his entire body with Ki attacks.

His grandfather wasn't very good at them, and preferred to rely on using physical attacks, but he'd taught Luffy enough for Luffy to get a good grasp on utilizing Ki.

Luffy had taken to such moves quite well. Ace was pretty good at them as well, but Ace didn't have the same urge to train as much as Luffy. Certainly combat training was something Ace loved, but just training his body? It wasn't something Ace was too big on, except to keep himself fit. But Ace had a natural power that allowed him to stay ahead of Luffy in strength. Garp said it was probably because both of Ace's parents had been of saiyan lineage, as opposed to Luffy, who only had a father with saiyan lineage.

But Luffy worked hard. And his Gum-Gum fruit enabled him to tank damage like nobodies business. Even Ace was hard pressed to beat him. Sometimes, Ace had to resort to using the same blackened fist that Garp used to hurt him.

Ace's was terrible looking in comparison to Garp's however, as Garp's fist would turn completely black. Ace's fist became splotchy with black marks, and then they faded instantly after contact. And he always ended up exhausted after doing so just once.

So, usually, Ace relied on ambush tactics, and back attacks, to get Luffy off guard. While stronger then Luffy, Luffy's ability to tank so much damage made it a chore to wear him out. So, instead, Ace used cheap tricks and dirty tactics to win.

Sometimes though, Luffy could swear he could tell when a back attack was coming.

Not that it mattered much anymore. Ace would be leaving in a few months. He'd turn 17, and then he'd leave to become a pirate. And then Luffy only had to wait another 2 and half years, and he'd get to leave and become a pirate. Garp was insistent that they become Marines, but, frankly, Luffy hated following orders. So did Ace. That's why they weren't going to be pirates on the same crew.

The only thing that would accomplish is both of them drowning at sea on a destroyed ship, fighting over who was captain. If they ever even made it off of Dawn Island.

~Two and Half Years Later~

Luffy stared at his dinghy. He had intended to build a proper ship, but, unfortunately...

Looking far the left, the tangled trees that he slammed together, rammed spikes into as makeshift nails, and threw a huge cloth over, slowly bobbed up and down, as it was caught in the inlet by two rocks.

When he'd asked Makino why it hadn't worked, she'd pointed out that it takes years to be good enough to build a ship, and could easily take weeks, or even months by a team of the most skilled shipwrights to actually build it.

So, instead of his masterpiece of a ship he had been so sure he could build, he'd be setting sail in a dinghy.

There was probably worse ways to begin ones journey to gain the title of Pirate King, and if he thought of any, he'd write them down to prove it.

"Alright!" Luffy grinned at Makino. "I guess I better head out now. Too bad about my awesome ship though. If I coulda built it the way I wanted, I'd ask you to be my bartender!"

She smiled. "I'd have had to decline, unfortunately. The pirate life is not for me. You have fun though. I hope you achieve your dream. I mean, I'm sure you will, but good luck anyways."

Luffy nodded. "Thanks, Makino!"

With that, Luffy set sail. He was barely out into the bay for five minutes before an old friend appeared. The same one that ate Shanks arm, when Shanks had saved him from drowning.

"Helloooo lunch!" Luffy shouted, his hands reaching forwards eagerly. The Sea King, sensing it's imminent demise, fled.

"Awwww." Luffy pouted, before his grin came back. "Oh well. Go, boat! To the Grand Line!"

The boat, understandably, did not respond.

~Prologue End~

There's the prologue.

Since, no doubt people are going to be curious, I'll provide a list of relevant power levels. This chapter, only Luffy is relevant, but, to put into perspective some things, I'll list the average human on DBZ's Earth, and One Piece's Oceanus, as well as the average power levels of Giants, Fishmen, and Merpeople.

Power Levels:

Average Human on Earth: 5

Average Human on Oceanus: 50

Average Fishman: 500

Average Merperson: 250

Average Giant: 5,000

Luffy: 3,259