Troublesome Brat.

Grand line, Marineford. At one of the docks, filled with supplies and docked Marine ships. One Seaman First-Class with black hair and eyes sitting on the port, dangling his legs at the edge. A thoughtful look on his not handsome but above average face while looking at his own reflection.

'That shitty god was telling the truth after all.' He sighed heavily.

Just few hours ago he was in front of a self-proclaimed God of Otaku after his unfortunate death and got the chance of reincarnation. Like any other neet he was excited at that but there is no free lunch in this universe.

Otaku God didn't give him any wish or chance to choose where he wants to reincarnate. God only told him about his own experiment about changing the plot of Manga's or Anime's he loves. Sometimes he would send unfortunate mortals to the said worlds and have them change the world however they want with the powers they got and watching over them with great interest, even interfere at times.

'Why didn't I get one of those kinds old god that gives MC whatever he wants or one of those beautiful Goddesses that fall in love with the most average mortals. I don't like being a guinea pig.'

While complains about the god he got, his situation isn't that bad per say. He woke up in world of One Piece, one of his favorite Manga, and being A Marine on top of that. As he was a police Officer in his old life, he prefers being a Marine over a Bounty Hunter or a Pirate.

'All will be better if this thing works though.' He said, looking a blue game-like screen floating in front of his face, few feet away.

[System: Requirement not met; system will be on hold.]

"At least tell me the requirement…" He shook his head and stood up. Then he noticed that pier he was sitting on getting really rowdy. Marine's running around, loading supplies to the large battle-ship docked.

He looked and saw a particular figurehead. A dog head with a bone in its mouth.

"Wait isn't that…" he took few steps back to get a full view and bumped at somebody. Somebody with a very large body from what he felt.

"Hmm? Who are you brat? Which unit you belong to?" a somewhat cheerful voice asked him.

Young boy quickly turned around and saw large man in white suit and vice-admiral coat hanging on his shoulders. He was Monkey D. Garp, the Marine Hero and maybe the strongest person on earth with Gol D. Roger's death.

"Seaman First-Class, Duke! I got promoted today, I don't get assign to a Unit yet, sir!" now named Duke, quickly saluted the Vice-Admiral. Inside Duke was giddy as Garp is his favorite character from the show, he never thought he would meet Garp this early.

Garp ruffled Duke's head and walked past him. "Then get ready brat, we have pirates to catch!" he laughed out loud and boarded the ship, Duke following him quickly behind, his eyes sparkling. He thought he needed to rose in ranks before working under such a legendary figure but who can guess what a Monkey thinks, right?

After a while, ship got ready and set sail from the half-moon fort. from what Duke learned, a new but strong pirate causing trouble in a non-important island, and Garp got assigned to check it out. He also didn't find any bounty from straw hats so maybe Luffy set sail around this time or it is still early in the plot.

"I should have read about the timeline more…" Duke shook his head. He only knows the events but not the years.

While sailing to their destination, Duke decided to train his body and get used to it. From the start he saw how strong this body is from his old one, even though he trained for years in his old life. This is the One Piece world to you.

He also learned about this body from the memories he got. The young man he possessed also called Duke and was a genius in his own right. So young but got accepted to Marine headquarters right away and rose in four ranks in just few months.

While he was lost in thought, instinctively training, Garp was watching him from afar. He looks at his right-hand man, Bogart, and asks.

"Who is that brat?" while Garp is an air-head, he is an air-head that lived life full of battles. He can see potential in people and Duke has quite a bit if you ask him.

"He should be the new rookie people talk about. Came to the HQ five months ago from North Blue and rising through ranks ever since. I'm grateful that he joined Marines than becoming Pirate like other people."

"True." Garp nodded. In this Great Pirate Age, everyone with bit of strength chooses to become pirate and search for the One Piece. It is very hard to find good kids to train as Marines these days.

Garp snorted and walked towards still training Duke. While latter was doing push-ups, Garp stepped on his back and yelled. "Go lower you brat!"

Duke wanted to snap at the old man but a fist to the head shut him up quickly. He continued to train while getting kicked or punched time to time when he made a mistake.

Now Duke understood how Luffy became so durable. Garp's training is anything but normal. He would not instruct like other people but kick you until you fix your mistakes. Then came the meal time which Duke also learned why portions of this world are so extravagant. Human body of One Piece needs very high number of calories to sustain itself, not talking about training ones. Even he ate at least 6 peoples worth of food after just few hours training.

This became daily cycle for four days then they finally reached their destination. An island called Seashell Island because of its beaches full of seashells instead of sand. Island has only one town, or used to be, and now it is occupied by The Snake Pirates. Their Captain Cobb has a Zoan devil fruit allow him to turn in to a giant rattlesnake.

The moment ship anchored at the beach; dozens of pirate mobs swarmed at it. First low-class Marines, such as Duke, opened up fire with their rifles, thinning the numbers then every Marine aside skeleton crew rushed to the town.

Duke not wanting to be left behind also rushed at top speed. Instead of a standard Marine sword, he chooses two knives to fight with. He still needs to learn how to use sword skillfully. But with two knives he still did a pretty good job.

He dashed and cut the legs of the pirates, taking advantage of his still short stature. When pirates fell into their knees, he simply cut their throat. While killing such ease would trouble any person from modern age, other than mentally ill people, Duke doesn't have any problem with killing criminals, especially ones that destroyed a town days ago.

While he was in heat of battle, a notification at corner of his eye catches his attention.

[System: Requirement; 'First kill' is achieved, system will be booted up now.]

[%5…%11…]

With every kill he got, system proceed to booting up. After his 13th kill, system finally became online but it is not what he expected from a classic system. He thought he would get one of those system he read in webnovels that allows protagonist to rose in levels and earn skills but instead he got a big roulette, filled with all kinds of powers he read or watched in his old life.

[Please roll the roulette to determine your power.]

[Warning: every power in the roulette will be adjusted according to the world host is residing in.]

'So, whatever I got will become a Devil Fruit? Is this what the warning all about?' he thought, but not that bad of a disadvantage if you ask him. While he would prefer without sea curse but you can't have everything you want right?

First, he made sure he was in a safe place and then rolled the roulette. He could see chakra, pride sin, sharingan, almost every power you could imagine, is in the roulette. After few minutes of rolling, roulette finally slowed down on a specific power, a power that made Duke having a coughing fit.

[Congratulations, host earned 'Shadow Monarch' as his power.]

A picture of a huge, muscular humanoid with glowing flame-like purple hair, glowing purple eyes, two curved black horns, and sharp claws stared right back at him. It wore a set of jet-black armor that covered it from head and toe and a long, flowing black cape.

Without giving him any heads-up, system injected the power to Duke, wrinkling his body with unimaginable pain.

"Guah! What the fuck?! I thought it would be devil fruit! Why it hurts so much!" his whole body start to emit black smokes, covering the ground he is standing on. His black eyes start to change and got a bright violet color, almost shinning.

At the same time, information about the power he got injected into his brain like how Sabo learned to use Mera Mera no Mi right after he ate it. He also learned more about his fruit.

Shadow Monarch, became a special-paramecia just like Katakuri's. It didn't turned Duke to shadow element but he can shape his body to evade attacks just like logia would but needs concentration.

Instead of Mana like from Solo leveling, Duke spends his stamina to extract shadows from his prey and control them. Stronger the target, more stamina he needs to expend. Also regenerating shadows uses stamina too. This could be weakness if his shadows destroyed in a mass.

After few minutes, his pain lessens, allow him to think normally again. He looked at the distant battlefield and saw it is still going on without slowing down. Snake Pirates are not strong aside from their captain but numerous, rivalling stronger pirate crews with their sheer number.

Duke approached few pirates he killed and saw black smoke rising from their body, waiting him to give the command. With a large grin he said.

"Arise."

Immediately black shadow hands burst from the corpses, rising from the ground. What Duke noticed is that instead of the shadow versions of the dead pirates, he got knights just like the ones from the webtoon.

'Why though? Sung Jin-Woo had knights just because he killed hundreds of knights…' as if hearing him, System answered for him.

[Answer: System read through Host's memories and adjusted the base shadow form accordingly. Host can change the basic form if he wants. Be aware that changing base form will be irreversible and permanent.]

'So, the question is do I want stinky shadow pirates or cool shadow knights?' Duke asked himself sarcastically.

He snorted and continued to extract shadows from his kills. It is pity that he can't extract shadows from other corpses. It has to do with his devil fruit though.

'Maybe awakening this power will allow me to extract shadows from every corpse.' Noting this at back of his brain, Duke finished his preparations. After ordering his summons to enter his shadow, he ran towards the center of the battle, where pirate captain in his hybrid-form, fighting Bogart.

From aside Garp saw Duke rushing recklessly without any weapon and wanted to stop him but stopped when he saw the confident look on the young boy's face, also weirdly his eyes were violet rather than black.

Duke got right at the center of the battle and expanded his shadow all around him for tens of meters. Battle stalled for a second when the ground became pitch black.

"What the he-"

"Oi, who's doing is t-"

"You Marines think some darkness will scare this cap-"

Pirates were running their mouths of when dozen shadow weapons emerged from the ground, impaling them to death. Not even their Captain escaped it. But it didn't end there when dead pirates exploded in shadows and new knights emerged from it, cutting down pirates close to them instantly.

Marines seeing that knights don't targeting them, continued to their attack. Garp and Bogart looked at the center of the shadow and saw Duke panting, but still standing.

"Just when that brat got a devil fruit?" Garp asked himself. Looking at the knights. He also saw that when a knight got killed, it would simply regenerate but looks like this tires Duke intensively.

Couple minutes later, battle concluded with Marines overwhelming victory. Every pirate got slain by either Duke's knights or Marines. At the end of the battle, Duke couldn't continue and just collapsed from exhaustion.

Before he hit the ground, Garp appeared beside Duke and grabbed him. "Arrange a room for him. I want doctor to check for side-effects. Others quickly clean up the field and look for survivors from the town!"

Without missing a beat, everyone gets to their work like clockwork. Garp looked at the sleeping Duke.

"Why every brat I met is so troublesome?" and returned to the ship.