Naruto had consumed the golden blood of Hades, forging an irreversible connection with the Lord of the Underworld. As the contract solidified, an ominous mark burned itself into his back—a blazing skull adorned with a crown, an undeniable symbol of his bond with the immortal of the dead.
The moment the contract was completed, Naruto's body underwent a dramatic evolution. His cellular structure became denser, surging with newfound power, while his chakra quality ascended to an unprecedented frontier. Where normal chakra was as weightless as gas, and high-quality chakra took on the density of mist, Naruto's was already on the verge of liquid before this transformation. Now, it had fully liquefied—a heavy, flowing energy that doubled his reserves and amplified his raw strength.
Just by altering his cellular makeup, Hades had propelled Naruto's base form to a level approaching that of Juubito. Yet, this was merely the beginning. Hades had promised an inhumane transformation, and Naruto was about to learn what that truly meant. He had signed a contract with the immortal of the dead—but he hadn't anticipated that the price would be absolute suffering.
At first, Naruto marveled at his new strength, reveling in the sensation of power coursing through him. But his moment of awe was cut short when Hades—unmoved by sentiment—shoved him into the eternal flames of the Underworld.
Naruto barely had time to react before the infernal heat engulfed him, searing through flesh and bone. Shadowy figures began to emerge from the flames—flame demons, manifestations of the eternal fire itself.
"Don't resist. Let your body adapt," Hades instructed, his tone completely devoid of sympathy. To him, this was simply a natural step in evolution.
Unlike his medieval appearance suggested, Hades possessed knowledge beyond mortal comprehension. He understood the science of adaptation, how the body could be pushed beyond its limits through controlled suffering. The human body, especially one as enhanced as Naruto's, could evolve infinitely—if it was subjected to the right horrors.
Naruto hesitated but ultimately submitted to the torment. His clones continued training in the outside world under his other mentors, but he created a single true clone to act as his proxy—one that held half his real power and wouldn't disappear even if he lost consciousness.
Then, he dropped all his defenses.
The agony was instantaneous.
The hellfire gnawed at his flesh, reducing skin to cinders, boiling his blood, and melting muscle off his bones. He should have blacked out—but the flames denied him that mercy. This was no ordinary fire; it was a living force, intelligent and sadistic. It calibrated its intensity to ensure maximum suffering, accelerating just as his body began to adjust.
For a moment, the pain would dull slightly—a fleeting reprieve—but then the flames would roar back stronger, adapting to his adaptation.
Naruto's screams filled the abyss.
The Battle That Never Ends
The flame demons attacked relentlessly, as if the inferno itself had willed them into existence. Each one was a mirror of Naruto's own power, wielding different combat styles and strengths. It was an endless war, fought within an eternal inferno.
Naruto lost limbs repeatedly, watching as his arms and legs were charred away before regrowing, only to be burned and severed again. Even his bones melted at one point, leaving him a husk that barely held together.
The flow of time became meaningless.
Seconds? Hours? Days? He didn't know anymore. All he knew was pain.
It wasn't until his adaptation reached an impasse that Hades finally retrieved him from the pit. His body had surpassed the initial stages, and the rate of improvement had slowed, signaling that it was time to move on.
Collapsing onto solid ground, Naruto struggled to breathe, his throat raw from screaming, his muscles aching from the relentless battles.
"How long... was I in there?" he rasped.
Even speaking was difficult—his insides had been burned and rebuilt so many times that they barely functioned as they should.
Hades merely looked down at him, impassive.
"Long enough."
Naruto had stepped onto the path of a true conqueror, but at a price no mortal would willingly pay. He was no longer human.
A full month had passed since Naruto had begun his training, though to him, it felt like years of grueling endurance. Every moment had been a test of his body's limits, yet now, as he stood before Hades, the results of his suffering were made clear.
"It's been a month since you started, and you have reached a stage where even a flame capable of erasing a mountain wouldn't burn you," Hades stated, his voice carrying a tone of measured approval. His piercing gaze studied Naruto, gauging both the physical and mental changes in the young shinobi. "If you want exact figures, your body can now endure at least 50,000 degrees Celsius without enhancements. How does it feel? Can you recognize the changes yourself?"
Naruto exhaled slowly, allowing the information to sink in. Fifty thousand degrees? The number was staggering. He had braced himself for the pain and suffering of the training, but hearing such a quantifiable measure of his resilience made it all the more real.
He closed his eyes and focused inward, analyzing his own body. His cellular structure had undergone a profound transformation, his very flesh and bones now denser and more robust. His regenerative abilities had soared beyond anything he had imagined. His chakra, which had always been a fundamental part of his growth, had been completely removed from the equation—Hades had deliberately forced his body to evolve on its own, without relying on any external energy.
"I can see it," Naruto admitted, flexing his fingers as he tested the strength in his grip. "But I don't think most people could survive this training."
Hades let out a small chuckle. "It might seem that way, but in reality, anyone can survive without permanent damage." He met Naruto's gaze, his smirk fading into a more serious expression. "I am an expert of the soul, Naruto. There is no way I would let my training inflict irreversible harm. Pain, suffering, and exhaustion—these are merely the price of evolution."
Naruto nodded, absorbing the words. As much as he hated to admit it, Hades' methods had worked. His body had transcended human limitations, and this was only the beginning.
"For now, you can take a short break and return after a day," Hades continued. "We'll keep going until you have completed the basic stage of this training."
A break. The very thought made Naruto's body sag slightly in relief. Then, suddenly, something clicked in his mind. The Uzumaki clan!
"Oh damn," Naruto muttered, his exhaustion momentarily forgotten. "I completely forgot about settling the Uzumaki on Uzu."
Hades gave a small wave of his hand, dismissing Naruto's concerns. "You don't need to worry about that. Only a single day has passed in the real world. This dimension's time operates on a different scale."
Naruto blinked. "Wait, so you control time?"
Kurama, who had been silently observing while indulging in the various books provided by Hades, finally chimed in. His deep voice carried undisguised curiosity. "Does that mean you have mastery over time manipulation?"
Hades let out an amused hum. "Mastery? Hardly. It's just a minor skill that allows localized time acceleration. Nothing too impressive."
Both Naruto and Kurama exchanged glances. To them, this was nothing short of immortallike.
Naruto exhaled, gathering his thoughts. "Will you guide me so I can better harness my power?"
Hades nodded, but instead of answering immediately, he turned his attention to Kurama. The fox had been observing everything from within Naruto's mind, but now, Hades seemed to be suggesting something unspoken.
Understanding the silent invitation, Naruto stepped aside, leaving Kurama to learn under Hades' tutelage. As much as the fox had grown alongside him, there was still much even a bijuu could learn.
Naruto rejoined his team, finding them in various stages of exhaustion, but determined. After witnessing his progress, they had all subjected themselves to the same hellish training, pushing themselves far beyond their limits.
With their moment of rest over, the next stage of their training began.
First came the Ice Trials, where Naruto was placed in an eternal frozen wasteland, the frigid temperatures biting deep into his bones. Unlike the fire training, which had gradually increased in intensity, the ice trials started at an already brutal level, pushing him harder now that his body had become sturdier. His regeneration worked overtime, adapting to the frostbitten agony that threatened to tear his limbs apart.
Once he conquered the cold, he was thrust into the Wind Domain, where gales sharp as blades cut his flesh apart, slicing through him again and again. Each wound forced his body to heal faster and stronger.
From there, he entered the Lightning Fields, where thunderbolts rained upon him without mercy, each strike sending millions of volts through his body. His nerves screamed, but he endured. Every spark, every shock, every surge of electricity forged his body into a living conductor of power.
After lightning came the Gravity Zone, where Naruto was subjected to crushing gravitational forces. The weight pressed against his body, threatening to snap his bones, yet with every second, his muscles adapted.
But the final trial was the worst of all—The Darkness Zone.
Unlike the physical tests, this trial was one of the mind and soul. In this place, Naruto was forced to experience the most despairing, horrific lives imaginable. He lived through thousands of deaths, bore the agony of countless failures, and was crushed under the weight of hopelessness.
It was a test designed to break him.
To shatter his spirit.
To force him to surrender.
Yet, he refused.
Naruto fought through the abyss, emerging from the void with an ironclad will. A powerful mind was needed to withstand true despair, for the mind shaped the body, and the body shaped the world.
As a final test, Hades exposed Naruto to diseases, poisons, and even the power of existence erasure. His body adapted to nearly everything—save for complete erasure itself. Still, even against that, his resistance had grown exponentially.
At the end of the six months spent in the Immortal Realm, Naruto emerged a changed man.
He was no longer simply a shinobi.
He had transcended the very limits of what should have been possible.
Over the course of six months—though, for Naruto, it felt like more than six years due to the sheer speed at which he operated—the young man had grown stronger than ever before. His body had undergone a transformation that defied human limits, pushing him further into the realm of the divine.
Naruto's healing factor had evolved to an absurd degree, accelerating to the point where injuries vanished the instant they occurred. Wounds sealed before blood could even spill, bones mended before they could fully break, and even complete disintegration no longer posed a threat. His regeneration had reached a level where as long as a single cell remained, he could reform his entire body.
This endless cycle of destruction and regeneration seemed to awaken something buried deep within his bloodline. His very biology responded to the ordeal, drawing out the latent potential of his ancestors. The Sharingan he had inherited from Sasuke had fully fused with him, unlocking its true form and granting him an ability that reflected his innermost desires. He had always wished for more time—to protect, to grow, to prepare. As if answering his call, his eyes gained the power to manipulate time itself, slowing the world around him while allowing him to move freely.
But that was not the only change. Naruto noticed that his base form was gradually adopting properties similar to his Six Paths Mode, granting him resistance to lower-class energy and making conventional attacks against him even more meaningless. There was also a more striking transformation—his hair had begun to turn white in strands, and strange, almost imperceptible bumps had started to form on his head. It was undeniable; his Ōtsutsuki heritage was stirring, awakening within him.
Recognizing the signs, Hades intervened before the transformation could fully manifest. The immortal of the underworld advised Naruto to suppress his Ōtsutsuki evolution for the time being. If he awakened now, it would happen instinctively, meaning the ability unique to his lineage would emerge without control. Instead, Hades suggested that Naruto first undergo genetic modification from Tsunade, ensuring that his body could adapt to the change and that he could harness his powers properly.
In these six months, Naruto had also deepened his understanding of the Immortal Realm, forming strong bonds with its inhabitants. His resilience, wisdom, and raw power had earned him widespread respect among the divine and legendary figures who dwelled there. Even Hephaestus, the famed blacksmith of the immortals, had forged grand artifacts for him at the request of Hades and Hestia—weapons and tools that would serve him well in the battles to come.
Though his time in the Immortal Realm was coming to an end, his training was far from over. Before leaving, Naruto ensured that one of his clones remained behind with Hades, continuing to absorb knowledge on both leadership and combat. With this preparation in place, he finally set out to reunite with his people—the Uzumaki Clan—ready to take the next step toward his destiny.