After consuming a Devil Fruit, a person's body undergoes a profound transformation. The natural energy of the world rewrites their very physiology.
At its core, this phenomenon isn't too different from Sage Mode.
But unlike Sage Mode, this transformation is permanent—and nearly irreversible.
More importantly, it grants the user unique abilities: vibration, combustion, transformation, and more.
Essentially, the Devil Fruit forcefully alters the user's body by infusing it with this world's natural energy. The benefit is immense power. The cost? A deep, primal weakness to the sea.
Naruto, through his keen observation and insight, quickly grasped the underlying principle of these powers.
In his eyes, Devil Fruits were a kind of permanent Sage Mode, unique to the pirate world.
But then a question emerged in his mind:
Why does Haki counter Devil Fruit users?
The answer, he reasoned, was that Haki is a pure form of natural energy, completely without attribute or element.
It's this purity that allows it to suppress the more flamboyant and specialized energies of Devil Fruits.
That said, Haki doesn't automatically overpower Devil Fruit users. Its effectiveness hinges entirely on the user's strength and will.
In other words, it's not the powers that clash, but the people who wield them.
Take Kaido, for example. His Haki was immense—he even claimed it to be the greatest force in the world.
And yet… he was still crushed by Luffy in Gear 5.
It could be said that Kaido was simply unlucky that day.
Naruto grew more and more interested in this concept of a "permanent Sage Mode." If he could decipher it, perhaps he could master it too.
He also recalled that Vegapunk, the genius scientist of the pirate world, had managed to replicate Devil Fruits artificially.
That alone implied a deep understanding—a glimpse into the true nature of this power.
The secret, Naruto believed, lay in something called the "Lineage Factor." When someone eats a Devil Fruit, it doesn't just grant power—it rewrites their genetic code.
This transformation is only possible because of the unique natural energy that saturates this world.
Naruto had been working tirelessly to become stronger. Using his heightened perception, he constantly studied the fine changes within Luffy's body.
After all, he could already activate Sage Mode at will and absorb natural energy from his own world.
But the natural energy here felt… different.
So, what happened when Naruto tried to absorb it?
Nothing. No transformation, no trace of Haki. He'd even tried forcing it—but still, nothing.
He came to a realization: Haki, too, was a product of this world's natural energy. But it didn't just come from nature. It only emerged after merging with the human body—a kind of catalyst reaction.
Naruto could still enter Sage Mode, but it amounted to nothing more than storing raw energy—no form, no effect, no technique.
He needed a formula—a means of converting this formless power into a defined, usable force.
Something to turn that raw energy into Haki, or even unique powers like Devil Fruit abilities.
He needed a key—a way to unlock the true potential of this world's power.
And that's why he continued observing Luffy—hoping to derive the "formula" behind the Nika Fruit.
Naruto frowned, a slight discomfort flickering in his expression.
"As expected of a Devil Fruit only the protagonist can wield. It's the most chaotic ability I've ever seen," he muttered.
"I've been studying this for so long… and even with my insight, I've only cracked 20% of it."
A crooked smile tugged at his lips.
It was absurd—this fruit truly defied all logic. Unlike ordinary Devil Fruits, this one felt like the embodiment of freedom itself.
Any other fruit probably would've been unraveled long ago.
But something else excited him: as he got closer to understanding it, the pace of decryption accelerated. With each step forward, his ability to decode similar powers would become sharper.
Naruto was confident: if he encountered another Devil Fruit user in the future, he might be able to unravel their powers with just a glance.
"So, what exactly is a Fruit Awakening?" he asked aloud, blinking in confusion.
To understand that, he needed to see someone who had already achieved it.
Someone like Katakuri… or Doflamingo—those rare individuals who had reached the next stage of their abilities.
Naruto was sure of one thing: if he saw them fight, he'd understand.
"…No point getting ahead of myself. One step at a time. First, let's crack the power in front of me."
Naruto muttered to himself, genuinely curious to see what would happen once he fully deciphered the power.
He activated a special Sage Mode, one adapted to the natural energy of the pirate world—eager to see how it would manifest.
In his mind, once the formula was complete, he'd be able to replicate Devil Fruit abilities directly.
If he could fully unravel the secrets of the Nika Fruit, he might even gain the ability to stretch and contort his body just like Luffy.
"…But in that case, I can't really call it Sage Mode anymore," Naruto mused aloud. "This is something unique to the Pirate World… tied to Devil Fruits. It's a different kind of transformation altogether."
While he was deep in thought, Luffy and Zoro were busy towing the boat forward—ropes strapped across their shoulders as they trudged through the sea. From time to time, Naruto would yell out to get Zoro to steer in the right direction.
Whenever their chakra reserves ran low, Naruto would restore them in an instant.
As their strange method of sailing continued, other passing ships began to notice the unusual trio.
After all, the boat was moving, but not with sails or oars—it was being dragged across the waves by brute force.
It wasn't that sails were useless… it was just that Naruto found human-powered propulsion more cost-efficient.
"…Wait a minute," Zoro muttered, eyes narrowing. "I've been doing this for hours. Why haven't I collapsed yet?"
"This kind of intense training… I should be completely spent by now."
He turned his head and noticed something odd—the sails had been lowered completely.
That meant the ship's progress was entirely due to him and Luffy pulling it.
Even worse, Naruto would occasionally shout, "Pick up the pace!" and make them sprint to accelerate the ship.
And yet—despite all that—he and Luffy hadn't passed out. They were still lucid, still moving.
Zoro's muscles screamed with pain. It felt like every fiber of his body was weighted down with lead.
It was like his very bones were weeping, urging him to give in and stop.
And still… he kept going.
There was even a moment where he thought he was hallucinating—the rope in his hand felt lighter, the ship seemed to speed up.
Then he saw Naruto standing calmly on the deck, his palms glowing faintly.
A strange energy surged from Naruto's hands and flowed directly into him and Luffy.
Suddenly, his fatigue vanished. His body felt rejuvenated. Overflowing with strength.
"…What the hell? That actually replenishes energy?" Zoro scowled, stunned.
"I've been dragging this ship for hours. How am I still standing?"
Naruto shrugged with a grin.
"Isn't it great? Training is all about breaking your muscles down… then letting them recover."
"You guys break them down faster—I'll heal them faster."
"Over time, that kind of compounded progress… it's insane."
His eyes narrowed slightly, a spark of mischief gleaming within them.
Truth be told, Naruto had even more extreme ideas.
Ideas that could only be described as hellish.
If they followed his plan to the letter, the gains would be exponential. They could reach new heights faster than ever.
And dragging ships across the ocean?
Well, it didn't have to be boring. In fact… he could make it kind of fun.