This is a Marine AU, featuring Ace and Sabo, and is part of a series of ASL AU stories that I have swimming in my mind for a while now.
This story changes a quite a bit of canon. For one, Ivankov will be in Level 6, not level 5. Also, all events pertaining to Luffy stays as per normal, he sets out at 17, meets his crew, and gains allies. Except, he doesn't meet Ace at Alabasta, Ace is not a part of the Whitebeards, yet, and Ace's execution doesn't happen. Marco basically replaces all those. Ace is protected in the marines, with no one knowing his true identity except Sabo and Garp. Those who found out, well, don't live to spread it. Sabo can be a devious, cunning little shit. Sabo also doesn't get taken in by the Revolutionaries. They treated him, but then brought him back to his brothers.
Luffy doesn't bother to wonder why he hasn't heard from his brothers in 3 years, his mind always going to adventures.
Anyway, enjoy~

Chapter 1: Impel Down

He was exhausted. For the first time in a long while, Marco was physically drained. Shackled and chained with seastone, in the deepest darkest depths of Impel Down hell, it was beginning to look bleak. The "Cleansing", if you could even call it that, really took a toll on him, even more so when it involved boiling sea water. He didn't scream however, and took it without flinching, but that does not mean that it didn't hurt. They really had no mercy on devil fruit users in level 6, do they?

As Marco sat there, in his dank and dark cell, with only a weak, dimly lit, pathetic excuse for a lamp on the wall outside his cell, and thought back, back to his capture, back to where it all started.

*Flashback*

It had been going smoothly. The day was bright and clear, the deck of the Moby Dick was a flurry and frenzy of action. Filled with his father's booming, hearty laughter, and the chatter of his many siblings, it was one of those days.

Thatch had recently been sent out on a mission to one of the islands under Pop's protection, and was due to return today. Marco felt a tug on the corners of his lips at the thought of his dearest and closest brother, no matter how much of a pain in the ass he could be -literally-. There was a shout from the Lookout stationed on Crow's nest. Thatch was coming home.

In half an hour, the little Sailboat had docked with the Moby, and Thatch climbed aboard to the roaring welcome of his brothers. Marco watched from his spot by Pop's chair, a fond smile in his eyes as Thatch greeted, bantered and laughed with his family. It was as if he never left.

"Gurararara! Welcome Home, Son!" Whitebeard's warm voice reverberated throughout the ship.

Thatch's eyes focused upon him. "Pops! Marco! How are ya, you feathered pineapple." Thatch bounded over to Marco and slung an arm over his shoulder, ear-splitting grin lighting up his face. "Miss me?"

"As if, yoi. I managed to get more work done without your constant annoying ass badgering me all the time." He smirked, for once not minding the jab. Thatch mocked-gasp and placed a hand over his chest, the other clutching a wooden chest under his arm. "Why, Birdy, how could you! You love my ass, admit it!"

"Burnt and on a stick, maybe." But there wasn't really any heat to it.

"Gurararara! Good to have you back, Son!"

"Pops!" Thatch turned to Whitebeard. "It's good to be back. You wouldn't believe what I found!"

There was an excited gleam in his eyes that for a moment had Marco wondering if he should be afraid. No, just no. Marco wasn't afraid, he never was. He was still curious, however.

"Well, yoi? What did you find, yoi?"

Thatch grinned, patting the box under his arm. "A devil fruit!" With that, he opened the chest and brought out, sure enough, a genuine devil fruit. It was purple, with the trademark swirls adorning its surface. It was round, shaped almost like a bunch of large oversized grapes.

"See, Pineapple? It looks just like a pineapple!" Thatch crowed. Does it, yoi? Marco wondered.

"So I thought of you and decided to take it!" Thatch frowned. "I don't know what it is yet. Haven't had the chance to find out." Then he brightened, "Oh, but I will tonight!"

"Zehahahaha!" Marco could never explain it, but from the first moment he had heard Teach's laugh, he had always had a slight shiver running down his spine. He had always brushed it off, and simply chalked it up to the unusual manner of laughter. After all, Marshall D. Teach was their ship-brother, and would never harm them, right? Right.

"Nice fruit you've got there, Commander Thatch. What are you gonna do with it?" Teach plodded over.

Marshall D. Teach had been a strong candidate for the Second Division Commander, but had refused on the grounds that he was not ready yet. The position had then been given to a member of the second division, Davi Jonez.

"I don't know, Teach. First, I have to find out what fruit it is first. Then, well..." He shrugged. "I will sell it. I don't wish to lose my ability to swim, and I can survive just fine without a devil fruit."

"Gurararara, You can do with it whatever you see fit, Thatch. You found it after all."

Thatch grinned, "Right!"

Then, celebrations proceeded and Thatch was soon surrounded by all his ship mates and his fellow commanders.

Marco couldn't put a finger on it at the time, but he had seen something in Teach. A glint in his eyes that since then, had been lingering in the back of his mind. Marco had, as with everything he had done when it involved Teach, shoved it aside and away. Now, when he thought back on it, it had seemed so obvious. That gleam in Marshall D. Teach's eyes had been malicious, cruel, evil.

He had been too ignorant, too relaxed, and didn't consider the possibility of a betrayal; couldn't even fathom it. He had been too confident, too reassured that the prospect of family, with Pops, was enough to contain and control any thoughts of defection.

Marco had paid dearly for that oversight, a cost so high, it ate away at his heart, and his mind. For he was the First Division Commander, the first mate; how could he not see it coming? He should have been stronger, faster, and more alert. Then maybe, just maybe, Thatch wouldn't be comatose, and fighting for his life.

…

A flash and boom of thunder startled Marco awake. When had he fallen asleep? A storm must be approaching, judging by the sound of the thunder. Marco gave a tired yawn and looked beside him on his double bed, the person he was expecting to be there, wasn't . Marco gave a little stretch while wondering where Thatch could be. It was the middle of the night.

He got up out of bed, leaving the warm confines of the comforter, and instantly felt a sort of fatigue wash over him. He ignored it and left his room, with the intent of searching for Thatch. His bed wasn't quite as warm as it was supposed to be.

The climb up to the deck of the Moby was the longest flight of stairs he had ever taken, or so it had seemed, at that point in time. Marco will never forget the sight that he saw when he finally came up on deck.

The image of Thatch's blood-soaked, still body sprawled out on the deck would be forever seared into his memory, and haunt his dreams.

Marco didn't remember much of what had happened afterwards, it all blurred and blended together in cacophony of colours, figures and voices. Marco only remembered his scream of shock and anguish. Had that really been him? He remembered the blood rushing to his head, the racing of his heart, and the cold sweat on his hands and the blood. Oh god, the blood. It was everywhere, on the deck, on his clothes, on his hands. The blood…had been Thatch's.

All Marco could register was the news. News that Thatch was currently fighting for his life, that Teach had been the perpetrator, had betrayed them, and blinding, overwhelming anger; and the thirst. The thirst for revenge.

The phoenix in him had cried out, had sung for blood, the blood of the culprit who had injured its mate so.

Unheeding to his Pop's words, so blinded by grief and rage he had been, Marco had chased after the traitor. Intent he was, on settling the score. The phoenix had thirsted for vengeance, and the thirst would not be quelled until he had the bastard's head on a silver platter, and his beat up, burnt and charred body a blackened mess behind him.

How dare he, how dare that man! Thatch had been his friend, his brother, his partner, his-

Marshall D. Teach was not going to get away, for the Phoenix was on the hunt.

…

Marco had tracked him for weeks, from island to island, shore to shore. Until he had finally cornered that evasive little shrew, and battled.

The fight was short, but brutal. Teach, who now went by Blackbeard –not that Marco will recognize him as a suitable rival of his Pops, or even as Teach, the brother he had been. No, he will simply be known as Marshall, he didn't even deserve the D-. Marshall, had now had the Yami Yami no Mi at his disposal. The fruit he had stolen from Thatch. The fruit he had betrayed the Whitebeards for. Ridiculous, right?

Marco didn't remember much from the fight, but he did remember how it ended. It had ended with his loss, his devil fruit nullified by the darkness, and his capture. Which led him to where he was now, in the lowest levels of Impel Down, awaiting execution for being the first mate to the strongest pirate crew in the world.

*End flashback*

Even now, Marco could still see the blood that had tainted his hands, staining it an unforgiving crimson red.

Now, he had given his family even more trouble. Surely the news of his impending execution would have reached their ears by now. Surely they would drop everything and charge towards Impel Down or Marineford to save their own. There would be an outright war, and he would have caused it. How could he have been so stupid?

His eyes looked up, from where his chin had fallen towards his chest, too tired to lift his head. He caught sight of the figure that was occupying the cell directly opposite his. In the dim lighting, he could just make out scales, but couldn't discern the colour. The silhouette however, was achingly familiar.

Jinbe? Marco wondered what he was doing here. He wanted to call out, to speak, but the words caught and stuttered out in his parched throat. Marco closed his eyes as the sound of footsteps sounded down the hallway. Wait, footsteps? Wasn't Level 6 supposed to be a dark solitary confinement? What were footsteps doing here? In fact, who would be crazy enough to walk through the lowest, most desolate level of Impel Down?

He soon got his answer as the footsteps, heavy and strong, stopped right outside his cell door.

"You look like a pile of sorry shit." Was the voice that resounded in his ears, a deep calming baritone. Sorry? Yes, he was sorry for getting ahead of himself and causing his family trouble. Shit? Well, he supposed so, from his earlier "baptizing".

The door to his cell opened and then shut as the footsteps –man- entered his cell. What was he doing? Marco didn't want anyone to see him right now, much less taunt him or jeer at him. He cracked his eyes open a little.

A pair of black ankle boots appeared in his vision where it was focused on the grimy cell floor. Then, a green object was thrust into his face, the familiar sloshing sound of water like music to his ears. The mouth of the green object –canteen, his brain languidly supplied- was pressed to his lips and tilted upwards.

"Thirsty, aren't ya?"

Marco didn't answer as he greedily gulped down the life-saving liquid as it trickled past his lips, the water immediately relieving his parched throat.

"Woah woah there, Phoenix, not so fast. You will choke." The canteen was brought away from his lips, now almost empty.

Marco felt well enough to lift his head and look at his "saviour" as the man talked to him. "Don't worry, there aren't any den den mushi surveillance cameras here. 'Cause what can they see anyway, right? Which is why we can do what we do. Anyway, that must have been one hell of a fight against the Shichibukai Blackbeard, huh?"

So, Marshall was a Shichibukai now? Well of course he would be; handing Marco the Phoenix over to the marines was a sure-fire way to Shichibukai title and position.

Marco's half-lidded eyes travelled up, up and up. Past the black boots, the black pants, and the belt with an A on it, to the suit jacket, the opened collar and loosely hanging tie, to the tasselled coat that was very familiar, and then to the face.

Marco was shocked, staring right back at him couldn't have been a man past his twenties. In fact, he looked to be around twenty years of age, with freckles, and wavy black hair, and sharp silver eyes, a grin seemingly stuck on his lips, illuminated by the dim hallway torch.

What really threw Marco off however, was the Marine hat that sat atop his head. A Marine had spoken to him? Had given him water? Without any taunting or jeering? Was he hallucinating? Had Marco finally gone off the deep end to the point where he imagined a Marine, a Marine of all people, being nice to him? Maybe if he spoke, the illusion would fade.

His lips parted, and he managed to cough out, "Wha-what…?" His voice was too weak and hoarse for his liking.

The image simply grinned wider. Ok, nope, not a figment of his imagination, apparently. How…intriguing.

"So you can talk. Good good." Oh god, was this Marine playing with him? Did he give him water just enough for him to get his voice back? Enough for him to scream during torture?

Oblivious to his tumultuous thoughts, the Marine continued, "Now, you can answer some of my questions."

Oh god, please no.

Marco opened his mouth to tell the man, boy, the marine was literally a kid, to scram, but he was faster.

"What's the New World like?"

Huh? Marco blinked. That was not what he was expecting. As Marco struggled to wrap his head around the question and sheer incredulity of the situation, another set of footsteps sounded through the halls that made Marco tense. The Marine however, was nonchalant.

The footsteps this time, was lighter than the Marine's that was in front of him, but distinctively male. It was sure, with a sense of elegance and certainty. It was also getting closer to his cell.

The Marine in front of him shifted, turning around, to face outside the cell, allowing Marco to see who was coming, and also to see the rank of the Marine.

A Rear Admiral. A fucking Rear Admiral. What the fuck in all hell, is a Marine Rear Admiral doing in level 6?

Marco didn't have time to think, as at that moment, another Marine came into view in the dim light. This Marine was carrying a pail of water, which explains his slow, steady and deliberate steps. He had curly blond hair, smiling purplish-blue eyes and a burn scar over his left eye. A glint caught Marco's eye and oh hell, another Rear Admiral?! Could this day get any worse? Were they going to throw water on him? God, please no, it was cold enough.

The blond Marine, contrary to what Marco thought, stopped outside Jinbe's cell. Wait, what was he going to do, he had better not do anything to the fishman!

Marco was once again proven wrong, when the Blonde opened the cell door and made his way in. Blondie then set his pail of water down on to the ground and reached forward to undo Jinbe's muzzle. The muzzle prevented Jinbe from using his shark teeth to bite through the chains which were not seastone-made.

The Marine then crouched down, and gently lifted Jinbe's head while bringing the water up to his mouth.

"Here, Knight-san, drink." The Marine's voice was a smooth, soothing tenor. Marco watched as Jinbe drank the water from the admittedly large basin.

"Ah, Knight-san, you cannot drink so much all at once, it will be bad for you." The Marine took the basin away, still sloshing with water. "Let's put this water to revitalising your body, hm?"

The voice was gentle, and reassuring, and Marco could see the hint of a smirk twitching upon the lips of the Marine in front of him.

As the blonde proceeded to pour the cool water all over Jinbe's fishman skin, Jinbe's voice rumbled. "I need neither your charity nor pity, Marine brat." Despite his blatant exhaustion, Jinbe could still master the strength to throw a scathing retort.

So, the blonde marine was as young as the raven? And they were both Rear Admirals? Marco would have whistled if he weren't in the situation he was in.

The blondie countered evenly, "It's not charity or pity, it's called caring, Knight-san."

At this, Marco blinked, while the Marine in his cell cracked up, "Oh, you just got told, Knight!"

As the raven cackled, the blonde turned towards him, them. Marco could now see that the young man was indeed that, young; probably around the same age as the raven. He wore slightly loose pants, tucked into black knee-length boots, a vest, a black belt and was that a cravat? All rounded up with the traditional Marine coat, and of all things, gloves.

The blonde made eye-contact with him, grinned, and turned his attention to the raven. He then made a little shooing motion and turned back to Jinbe. The raven marine rolled his eyes, and turned back to face Marco.

The Raven grinned, a very familiar grin. In fact, both the raven and the blonde grinned like-

"I'm Portgas D. Ace. The blonde over there is my brother, Noah D. Sabo. We will be your "guards" during your time here."

Of course, but of course. They were both Ds.

Phew, done~ Please tell me what you think~
If you have any qns, please comment and I will try to answer them as much as I can without revealing too much such that I spoil the fun. uwu.
If you are wondering about Sabo's Last name, I came up with it myself. I wanted to be original, but didn't want to use Outlook as Outlook isn't a last name. Sure, Sabo's dad was named Outlook, but that was it. He was named Outlook the Third. That was all it was, a name, and a title, meaning that there were two more people named Outlook as well, before Sabo's father. Outlook wasn't the family name, it was a title given to Sabo's father. Hence, I gave Sabo the name Noah, after Noah's ark, which sailed the seas, the seas which Sabo, is often associated with.
Okay~ I hope you enjoyed~