There is no justification for Zenyatta showing up in the One Piece universe, he just does. Blame it on the Iris.

Robin had finally gotten a chance to sit down in the shade as the rest of her crew enjoyed the festival on this unknown island. Some of them enjoyed trying out all the food while others enjoyed the games. She cared not for such things but did enjoy people-watching now and again when her books weren't available. The only thing was that a peculiar robot occupied the other side of the table she sat at. It noticed her, gave a nod of acknowledgment, and went back to reading that day's newspaper.

It didn't seem to want to disturb the comfortable silence between them, but Robin's curiosity got the better of her.

"I've never seen a robot such as yourself before."

The blue lights on its head glowed for a moment as it regarded her. "I suppose that makes me rather unique in these lands." The newspaper in its hands lowered slightly as it gave her its full attention.

"Are you not from this island?" From what Robin saw, this island was relatively advanced, but nothing like Egghead with its massive cities with its own air conditioning or heating.

"Not at all. However, it has welcomed me kindly."

"If it's not too personal, I'd like to know where you come from then." The archaeologist rested her chin in her left hand. "Perhaps my crew and I could visit. At least, I'm sure the boys would like to."

The robot laughed at her question, but not rudely. "I am afraid visiting my homeland is impossible."

The woman frowned at this information. "And why is that? Too dangerous?"

It shook its head. "I do not have one. I prefer to wander."

"Why would you do that?"

The robot answered her with its own question, "Why do you wander the seas?"

Inwardly, Robin smiled. She could play that game. "To learn."

"Ah, I too like to learn."

"So, we have something in common."

"Indeed."

The conversation stilled for a moment as Robin took a sip from the tea she procured earlier from Sanji. The cup hit the table with a clink.

"What are you learning about?" She asked it.

"People. Culture. Architecture. Anything there is to see in this world. What of yourself?"

"I'd like to know about a certain period in history. One that has been lost to time."

"The Void Century?"

A nod. "The very same. Everyone knows about it yet knows nothing about it."

"The study of the Void Century is seemingly strictly forbidden. I know not of the reasoning as to why. History is doomed to repeat for those unaware of it."

This time Robin smiled for real. She was unsure if the robot could see her given it had no discernable eyes. "Naturally. Is it not curious that those in power seek to stop all attempts to uncover such a secret?"

"It does seem suspicious."

"Are you not weary of me for seeking the truth?"

At that, the robot seemed confused if the tilt of its head was any indication. "Why would I be?"

"Speaking to a criminal may brand you as guilty by association."

"I am well aware of who you are, Nico Robin." Robin's eyes sharpened, and it raised its hand in a gesture of peace. "Fear not, I do not seek conflict. I see what you are doing as quite noble."

"Is it?"

It nods. "Of course. Those who try to ban the procurement of knowledge generally have a reason to do so, justified or not."

Robin turned back towards the festival and the robot returned to its newspaper. A family of four distantly walked by, the parents chatting away as the two toddlers enjoyed cotton candy. It reminded her of Chopper.

While the two strangers continued their activities, the silence was broken by heavy footsteps and Robin smiled as she saw who it was that was approaching her.

"Ow! Robin, I've been looking for you. We're gonna head over to the theater they have here and Nami-sis wanted you to come."

"I'll be right there Franky."

Franky did his signature pose, "SUPER! I'll save you a seat!" His mechanical whirring grew distant as he walked away.

"I suppose this is where we part ways, robot-san."

"It has been a pleasure, Miss Robin. But please, call me Zenyatta."

Zenyatta was meditating on the beach as the sun began to set. He levitated off the sand as the waves rolled back and forth ahead of him. His orbs whirled around him and bounced in a rhythmic pattern. Unfortunately, the moment was broken when laughter could be heard as hurried footsteps broke through the tree line that bordered this beach.

"This is way more fun!" A young man with a Straw Hat laughed as he came barreling out of the trees, marines hot on his heels.

"Luffy, you idiot! Why'd you have to ruin the theater?!" A woman he hadn't seen before, orange hair, and most definitely furious if her tone was any indication.

"That play was boring!"

"We're in the clear on this beach, let's just fight!" A swordsman with a peculiar hair color, but deadly serious as he unsheathed two swords at his hip.

"Stop right there criminals!"

For a moment, Zenyatta hesitated to help as the fight continued. While the marines were the reigning authority on this island, and seemingly, most of the world, he knew they were not infallible. Just as with any government, there was always corruption. Yet he could not simply help what could be criminals for all he knew. That was until he saw Nico Robin fighting amongst the so-called criminals. Considering her reputation amongst the Marines, she certainly would not pick an unnecessary fight. She saw him and waved as she returned her attention to fighting against the overwhelming numbers. While she and her friends were powerful, the sheer number of marines was tiring them as time passed.

At one point, Zenyatta noticed a singular marine creeping behind Robin with his sword, as silent as a mouse, and he realized she was unlikely to react or receive help, given her position at the backline. Thinking quickly and calculating the trajectory needed, Zenyatta shot one of his orbs directly into the marine's head, knocking him out cold. The man fell over with an audible thud.

Robin turned in surprise to the downed man before looking over at the robot monk. He made a peace sign as he approached and the orb levitated back to him.

"Thank you for the assistance."

"No need." He told her. "I shall assist you."

"You didn't strike me as the fighting type." She noted.

"Looks can be deceiving, and the world is a dangerous place."

She hummed in agreement. "Then, shall we?"

"After you."

The two fought their own battles while covering each other. In the end, alone stood one Vice Admiral amongst the litter of his downed soldiers.

"I guess I'll stop the rest of you myself."

The Straw Hat man responded to his bravado, "Bring it on!"

The Vice Admiral smirked, "Very well. Prepare yourself for... -what is this?"

A purple orb hovered slightly adjacent to his head. "Darkness falls."

The man began to look crazed, attacking wildly at seemingly invisible ghosts with his sword. "Get away from me you freaks!"

The rest of the groups looked on in confusion as the man lost himself more and more before an orb got shot into his face which caused him to stumble. Then, a volley of them shot into his chest bringing him to his knees. Everyone except Robin turned behind them to see a floating robot shoot one final orb into the man's face, finally knocking him out. The orbs recalled themselves at a fast speed back to the monk.

"Is that a robot?!" The Straw Hat man exclaimed in wonder with stars in his eyes.

The orange-haired woman face palmed. "Not this again!"

"Greetings."

Robin smiled. "Let's get on the ship and we can do introductions."

The crew gathered around him and Robin as she introduced him.

"Everyone, this is Zenyatta. I met him earlier today before we all went to the theater."

Zenyatta did a small wave to them all. "A pleasure to meet Miss Robin's companions."

"Ooooh! My name is Monkey D. Luffy! I'm gonna be King of the Pirates!" Luffy was seemingly about to explode with questions but reigned himself in with a 'look' from Robin to behave himself for the time being. "Thanks for helping us!"

Everyone introduced themselves in one manner or another, but then came the boys and their questions.

"How are you floating like that?!" Luffy asked him immediately.

"Can you fly?" Franky, the cyborg he learned, questioned. "Were you made by Vegapunk?"

"What was that purple orb you put on that guy?" Sanji asked. "He was freaking out like crazy!"

Zenyatta put his hands out in a pacifying gesture. "All my abilities are gifts from the Iris."

"What's that?" Usopp asked, tilting her head to the side in confusion. "Is that some kind of Devil Fruit thing?"

The monk shook his head. "The Iris is a form of transcendence that all humans and robots can achieve. It all stems from my ancestor and progenitor, Aurora."

Luffy picked his nose in boredom. "Enough of that! Show us the cool stuff you can do!"

Nami chastised him, "He's not gonna put on a show for you!"

"It's no problem."

"Eh?" Nami blinked at Zenyatta's acceptance. "Seriously?"

Zenyatta nodded. Carefully, he plucked at a seemingly random orb from the ones floating around him. It glowed with a yellow hue and vapor, "Miss Nami, if you please would show me your arm."

Nami did so tentatively while the orb floated over to her.

"Oh no! My Nami-swan got hurt! Forgive me, my love!"

"Shut it!"

"Yes, my queen!"

The orb glowed a deeper yellow as a trail of vapor trailed onto the injury. Everyone gasped as the decently sized cut started closing itself all on its own. "Embrace tranquility."

Nami smiled in delight as the burn from the cut disappeared. "Wow! That's incredible! Thanks, Zen!"

"Think nothing of it." He responded as the orb floated back to him. "We are all one within the Iris."

Chopper excitedly walked up to him. "If you can heal others, are you a doctor too? I've never met a robot doctor before. Oh, that doesn't bother you, right? Calling you a robot?"

Zenyatta chuckled. "Not at all. After all, I am what I am. To answer your first question, I am not a medical practitioner. However, I am knowledgeable on the human body and biology, but I lack official training."

"Then, is that magic?" Chopper almost couldn't stay still at the thought of real magic. "Like a wizard!"

"What seems like magic is sometimes science we don't yet understand."

The reindeer contemplated the statement, "Wow, I never thought of it that way... maybe I could do it too!"

At that point, the swordsman Zoro stepped in front of the doctor. "I wanna know the same thing as the dumb cook-"

"Oi, you shithead!"

"That purple orb you put on that guy, I've never seen anything like that. What did you do?"

The monk thought of the best way to explain the ability in a manner everyone could understand. An idea came to him and he pulled both the yellow orb and the orb with the purple hue.

"Harmony," Zenyatta raised his right hand which carried the yellow orb, "it represents balance, peace within one's self, and being one with the world."

Lowering his right hand, he raised his left. It pulsated with a dark energy that made some members of the Straw Hats shiver. "Discord represents strife, discontent, and conflict."

Robin spoke up, "If my guess is correct, and that yellow orb heals a person, then does the other also deal harm?"

"Not exactly. It will not deal direct physical harm but gives one a mental battle. Were it not so unpleasant, I would demonstrate but that would be quite unwise."

Sandaled feet walked forward. "Try it on me."

Sanji immediately disagreed, "Oi Luffy! You shouldn't volunteer for something like this!"

Luffy shook his head and smiled. "There's all kinds of people we'll fight on our way to the final island. We have to be ready for anything! Lay it on me, Zen!"

Zenyatta stared at him for a moment. "Are you certain?" He asked simply.

"Yup!"

"Very well, but only for a few minutes." Zenyatta pushed the dark orb forward. "Bask in the shadow of doubt."

The crew watched on as the orb attached to Luffy. His smile abruptly vanished and he closed his eyes with a pained expression. For a minute, he made no noise. Then in the second minute, he opened his eyes with a haunted expression. Visibly shaken, the orb jostled off of him and hurriedly returned to Zenytta, its task accomplished for the time being.

Brook asked the question everyone was thinking, "Well, Luffy-san? What happened?"

Luffy took a deep breath before shaking his head and wearing a pained smile. "Don't worry about it, Brook!" Their captain's tone made it clear he didn't want to elaborate. There were some concerned looks thrown his way but they all dropped the subject.

"Anyway, let me ask you something, Zen."

"I do apologize for the feelings of discord brought about within you."

"Shishishi! Don't worry about that! I asked for it. But since you helped us out against the Marines, that makes you a criminal too!"

Robin made for an apology but Zenyatta held up a hand to stop her. "I was aware of the consequences, Miss Robin. Do not feel any blame."

Luffy walked toward him until they were face to face, he held out his hand and demanded, "So, join my crew!"