Emperor of Mankind (Naruto X Marvel )

The ocean depths were suffocatingly dark, a realm where light dared not venture. Only the faint bioluminescence of distant creatures broke the void, glowing like faint stars in an eternal night. Naruto and Kakashi descended further into this abyss, their senses sharp and bodies enhanced by chakra. Around them swam a myriad of monstrous beings—some large enough to dwarf whales, others small yet radiating dangerous auras. The water was alive with silent menace.

But none of these creatures held a candle to the one resting at the ocean floor. As the two shinobi approached, the sight of the Leviathan made even Naruto, used to the extraordinary, pause in awe.

The Leviathan was colossal, a sea serpent of unfathomable majesty. Its body stretched nearly five kilometers, a monstrous scale that dwarfed even the greatest Bijuu. Its golden and silver armor gleamed faintly, reflecting the dim light like a treasure hidden in the depths. The armor was not just ornamental but functional, with jagged fins and sharp protrusions designed to intimidate and defend. Its long, flowing hair moved like a living current, and its two tails ended in harpoon-like shapes that seemed built for piercing and ripping through prey.

Most striking of all was its face: two horns crowned its head, one massive and knife-like on its forehead, and the other smaller but sharp, jutting from the tip of its nose. Between them, the barrel of a cannon-like weapon protruded, its hexagonal cross-section promising destruction. Despite the creature's serpentine beauty, it radiated an overwhelming sense of danger.

Naruto closed his eyes briefly, sensing the creature's chakra. "Teacher," he whispered, his voice calm but excited. "It has enough chakra to rival Tsunade. Do you want me to subdue it?"

Kakashi's lone visible eye narrowed as he studied the creature. Even from this distance, he could feel its latent power, a life force so vast it seemed to breathe with the ocean itself. It was far beyond anything he'd encountered, larger and more imposing than the Kraken near the Land of Lightning.

"I'll leave it to you," Kakashi replied. His tone was light, but there was an edge to it—a quiet acknowledgment of the task's enormity. Kakashi wasn't one to pick unnecessary fights, and he had no intention of recklessly engaging a being of this magnitude. He trusted Naruto.

Naruto nodded, his face serious but tinged with excitement. He activated Senjutsu, allowing him to blend seamlessly with the natural energy around him. The two shinobi became invisible to the Leviathan's senses, their presence vanishing like whispers in a storm.

With a flicker of motion, Naruto appeared above the Leviathan's massive head, standing near one of its closed eyes. The serpent stirred, sensing something amiss. Its eye snapped open, revealing a piercing gold iris that locked onto the small human standing boldly on its armored body.

The Leviathan's roar began to build, a deep rumble that made the water vibrate—but before it could unleash its full fury, it froze. A crushing pressure descended upon it, emanating from Naruto. The serpent's massive body quivered, its survival instincts screaming at it to submit.

Naruto's chakra, vast and overwhelming, poured out like a tidal wave. The Leviathan, proud and ancient as it was, recognized the power instantly. This wasn't a mere human—it was something far greater.

"Hello," Naruto said calmly, his voice carrying through the water despite the lack of sound. "My name is Naruto Uzumaki, and I have a request for you."

The Leviathan's gaze narrowed, its mind racing. Though it didn't speak human languages, Naruto could see its thoughts and intentions through his enhanced senses. The serpent was wary, but the power difference was undeniable. It had lived for centuries by avoiding battles it couldn't win.

What do you want from me? the Leviathan's thoughts rumbled, its pride barely restraining its fear.

"I want you to partner with my teacher," Naruto said. "In return, I'll help you grow stronger."

The Leviathan's arrogance flared briefly. It glanced at Kakashi, hovering in the distance, and dismissed him as unworthy. I don't want to work with him. I'll serve you instead, the serpent offered, its tone desperate yet calculating. It had recognized that Naruto was far beyond anything it could challenge.

Naruto sighed, shaking his head. "I already have a partner," he said, summoning Kurama's image to the forefront of his mind. The fox appeared briefly, its crimson eyes glaring out from Naruto's aura.

The Leviathan froze, its confidence shaken. It had seen Kurama before—nearly a century ago, the Nine-Tails had unleashed a catastrophic explosion that had wiped out an island near its territory. That memory was enough to break through the last of its resistance.

"I'm offering you a chance," Naruto continued. "You'll work with my teacher, and together, you'll become something even greater. I'll help you reach heights you've never imagined."

The Leviathan hesitated for a long moment, its massive form coiled tensely. Finally, it lowered its head slightly in submission. I accept your offer, it thought grudgingly. The power Naruto displayed—and the promise of more—was too great to ignore.

Naruto smiled, turning to Kakashi. "It's done. He's ready to work with you."

Kakashi descended to their level, his body reinforced by chakra to withstand the crushing pressure of the ocean depths. His normally calm demeanor softened into something warmer as he patted Naruto's shoulder.

"Great work, Naruto," he said sincerely. "You've really grown a lot. I didn't expect you to negotiate with it."

Naruto beamed at the praise, feeling a surge of pride.

Kakashi's gaze lingered on the golden and silver armor that adorned the Leviathan's body. The metal shimmered in the faint light of the ocean depths, its luster unaffected by the passage of time or the crushing pressure surrounding them. He couldn't hide his curiosity. "What is this metal, and why is it part of the Leviathan? How did it come to be like this?"

Naruto blinked, caught off guard by the question. He hadn't considered the armor's origin, but now that Kakashi had brought it up, it seemed strange for a sea serpent to have such intricate and advanced protection. Turning to the Leviathan, he posed the question. "Do you know anything about this metal? How did it become part of you?"

The Leviathan's glowing eyes focused on Naruto, its ancient voice resonating within their minds. I do not know what the metal is called, it admitted. I found it deep within the ocean many centuries ago, buried in the ruins of an ancient civilization. When I touched it, the metal fused with my body, altering me. It forced me to grow into this form and granted me incredible power. Attacks that would once harm me now bounce off, and most are reflected back at their source.

There was a reverence in the Leviathan's tone, a mixture of respect and fear for the mysterious metal that had become a part of its very existence.

Naruto's curiosity got the better of him, and he decided to test the metal's properties. With a flick of his hand, he sent a weak wind blade toward the Leviathan. The blade bounced harmlessly off the golden surface, dissipating as if it had never existed. Intrigued, Naruto increased the number of wind blades, unleashing a barrage across the Leviathan's massive body. Every single attack was deflected, scattering harmlessly into the surrounding water.

Please, stop! the Leviathan's voice cried out urgently, tinged with fear. Do not test the durability further!

Naruto immediately stopped, raising his hands in apology. "Sorry about that. I just found it really interesting." He rubbed the back of his head sheepishly, his expression genuinely contrite.

The Leviathan's massive eyes narrowed slightly, its pride bruised. Under normal circumstances, it would have retaliated, but the power difference was undeniable. It swallowed its indignation, resigning itself to the situation.

Kakashi, meanwhile, studied the interaction with a critical eye. The Leviathan's armor was remarkable, and its ability to reflect attacks was beyond anything he had seen. But for now, they had a task to complete. "Naruto," he said, breaking the moment, "how about we start the process and see if it works?"

Naruto nodded, turning his attention back to the Leviathan and Kakashi. "Alright. Just don't resist and try to relax," he instructed. He stepped between the two and began the sealing process. Naruto had learned the method by watching Shukaku perform it, and the additional explanations he'd received afterward gave him enough confidence to proceed.

The Leviathan obeyed, suppressing any resistance as it felt the pull of Naruto's technique. Slowly, its massive form dissolved into pure energy, swirling like a vortex before being sealed inside Kakashi.

With the Leviathan's essence contained, Naruto moved to the next step. "I'm going to connect your souls and chakra now. Get ready," he announced, his voice steady and calm.

Kakashi and the Leviathan both felt it—their chakras intertwining, their souls merging into one cohesive entity. The process was seamless, their unique traits blending together. Kakashi's mastery over water and lightning jutsu fused with the Leviathan's inherent elemental prowess, enhancing their individual abilities to new heights.

The transformation was immediate. Kakashi's body grew to an imposing five meters, his figure clad in a magnificent suit of golden armor that mirrored the Leviathan's. The armor gleamed brilliantly, and small, elegant wings sprouted from his feet and helmet. A white cape billowed behind him, a stark contrast to the darkness of the ocean. In his hands, two blades materialized—sleek, curved swords that seemed to hum with elemental energy.

Naruto stepped back, marveling at the result. Kakashi's fusion with the Leviathan was a success. The combined power of the two wasn't on the level of a Bijuu, but it was still staggering. Kakashi had ascended to a level of strength where he could destroy mountains with ease and even obliterate an island if he unleashed his full potential.

Kakashi examined his new form, flexing his armored hands and feeling the surge of power coursing through him. The connection with the Leviathan was strange but not unpleasant. It was as if the serpent's thoughts and instincts now flowed alongside his own. "This… is incredible," Kakashi murmured, his voice slightly deeper, resonating with the Leviathan's presence.

Naruto grinned, his excitement palpable. "It worked! You're stronger now, and this is just the beginning. Once we help the Leviathan grow even more, your power will reach new heights!"

For the first time in a while, Kakashi allowed himself a small smile. "You've done well, Naruto. This was beyond anything I expected. Thank you."

Naruto's grin widened. This was more than just a step toward their goals—it was proof that they could accomplish the impossible. The fusion was a success, and with it, their hopes for the future burned brighter than ever.

Naruto's mind buzzed with thoughts about human limits and growth. It struck him as odd that so few shinobi had ever truly tested the full extent of human physical capabilities without relying on chakra or ninjutsu. Gai and Lee were exceptions, but even their feats might only scratch the surface of what was possible.

"Teacher," Naruto asked, breaking the silence as they rested after Kakashi's fusion, "what do you think is the limit of humanity in physical terms? How strong can we get just physically?"

Kakashi, still acclimating to the presence of Leviathan within him, mulled over the question. His power had grown significantly thanks to the fusion, but his thoughts drifted to his past. The raw power he'd temporarily wielded during the battle against Kaguya came to mind, a fleeting experience compared to the permanence of this new strength.

"I honestly don't know," Kakashi admitted. "No one's ever fully focused on pushing their physical capabilities to the extreme. Gai is probably the closest example. Without accounting for chakra, his raw physical stats are unparalleled. He can move at around ten times the speed of sound and carry over a thousand tonnes. That said, even he doesn't represent the absolute peak of human potential. The Hokage could have been stronger if she prioritized physical training, but she relied on chakra-enhanced strikes."

Naruto frowned at that. "So even Gai-sensei, who worked so hard, is still limited in some way? That doesn't make sense! Most Chunin can already move faster than Mach 10, and Jonin can carry way more than a thousand tonnes when they use chakra. Shouldn't we figure out what our limits are without chakra before trying to surpass them?"

Kakashi nodded thoughtfully. "You've got a good point. If we don't strengthen the base, we'll run into the same problem if we're ever without our chakra or if it's disrupted. But I don't have a solution. This isn't something most shinobi even think about. The best person to ask would be the Hokage. She knows more about the body than anyone else."

Before Naruto could respond, Leviathan's deep voice echoed in their minds. Why don't you try eating strong creatures? That's how we sea creatures grow stronger. The stronger the prey we consume, the more it enhances our bodies. Maybe it's because your kind only eats normal food that your physical strength barely improves.

Naruto blinked, considering the idea. He'd never thought about food in that way. Sure, he'd shared a meal with the Akimichi clan and seen their extraordinary abilities tied to their eating habits, but beyond that, food had always been just food. "Do you think that would really work?" he asked aloud, looking at Kakashi.

Kakashi raised an eyebrow. "It's not impossible. The food we eat does affect our bodies, though I've never heard of it making such a drastic difference. If we're talking about enhancing physical growth, this might be something to ask the Akimichi clan or even the Hokage about. They'd know more."

Naruto scratched his head. "Makes sense. It's worth a shot. Still, we won't figure this out tonight. Let's rest up and visit the Hokage and the Akimichi clan tomorrow morning. We'll figure out where to go from there."

Kakashi leaned back, feeling the quiet hum of Leviathan's presence within him. Naruto's enthusiasm and willingness to explore new ideas were refreshing. It wasn't just about gaining power—it was about learning, growing, and evolving. Kakashi smiled faintly beneath his mask, his thoughts drifting as the group settled down to rest. Tomorrow, they'd take their next step toward uncovering the true limits of human potential.