Devil Fruit abilities are absurdly powerful—especially the Nika Fruit. It's arguably the most outrageous power out there.
Luffy can inflate his bones to amplify his attack power. With a body like his, even the surge of chakra from opening the Eight Gates might not be too much for him to handle.
Even so, Naruto still warned him not to get reckless with it.
"Two or three gates at most for now," he advised. "Any more than that will overload your body."
After all, Luffy's overall strength still hadn't reached its peak. He might not be able to endure the burden of excessive power.
Take his Gear Second for example. When he first used it, it came with the risk of shortening his lifespan. But after two years of rigorous training, Luffy could not only use it at will, he could also intensify it in battle—eventually unlocking Gear Fourth.
That initial side effect—shortened lifespan—seems to have vanished.
The only explanation? Power always comes with a price, but if your body catches up, the risk diminishes.
Thanks to two years of training, Luffy's physique had evolved. That likely removed the drawbacks. And perhaps the early version of Gear Second was just incomplete—flawed. Through years of refinement, he'd perfected it. The same applies to Gear Third. Now his body doesn't shrink after using it.
But in this world, Luffy was still just starting his journey. He'd only recently begun refining chakra. Compared to the standards of a seasoned shinobi, he still lacked the necessary foundation.
Sure, his rubber body could mitigate some of the side effects of the Eight Gates, but if the intensity crossed a certain threshold, even he wouldn't be able to avoid irreversible damage.
Caution was essential.
Naruto gave it some thought. Looking at the battles Luffy might face in the East Blue, he realized… there wasn't much to worry about.
None of them really posed a threat.
Hawkeye Mihawk, the only exception, was absurdly strong. But they'd only met at the floating restaurant, and Mihawk clearly wasn't hostile.
Then there was Smoker in Loguetown—a Logia-type user. Without Haki, Luffy wouldn't be able to land a hit on him. That would be a problem.
Aside from those two, every other opponent in the East Blue was just small fry.
With chakra and the Three Basic Techniques—Henge, Kawarimi, and Bunshin—Luffy could steamroll through them even more effortlessly than before.
Feeling the chakra coursing through his body, Luffy fell into thought.
"Hmm... I think I can push it a little further," he murmured.
"My chakra's increased. It's flowing really fast..."
"What if I accelerate my blood flow too?"
The mechanics of the Eight Gates had sparked an idea in him.
Naruto's eyes narrowed.
He's already thinking about entering Gear Second?
He turned toward Zoro, who was still climbing trees—part of his chakra control training.
The guy was definitely putting in effort... but at this pace, it was too slow.
Naruto sighed. "I'll have to speed things up."
Efficiency was everything to Naruto. And sometimes, that meant bending the rules a little.
Their ship—the Fox Boat—drifted with the ocean current.
With Naruto aboard, food and fresh water were no concern.
But without a proper navigator, they had no set course. Their destination was left entirely to chance.
Naruto unrolled a sea chart.
As a ninja, reading maps was child's play.
Thanks to his advanced intellect, a glance was all he needed to figure out their general direction.
He rigged up some crude navigation tools and plotted a basic course.
No, he wasn't Nami. He couldn't chart a perfect route with absolute precision.
But given time, they'd get where they needed to go.
"We really need to find a navigator soon," he muttered, folding up the chart. It didn't interest him at all.
Sure, he could manage the basics, but he lacked the passion—and professional polish—for sailing.
"And we need a musician too!" Luffy added, grinning widely.
He seemed to have an almost mysterious obsession with the idea.
Naruto stroked his chin, lost in thought as memories surfaced from his past life.
Besides the main anime series, One Piece also had several theatrical releases. He vaguely remembered one in particular—a movie centered around Red-Haired Shanks' daughter.
She was a singer, wildly popular across the pirate world.
More importantly, she had once been Luffy's childhood friend.
Everything seemed to tie together now.
No wonder Luffy had immediately declared he wanted a musician as soon as he set out to sea. That desire must've been influenced—perhaps subconsciously—by her.
A subtle bit of foreshadowing, now that Naruto thought about it.
"You just said we should increase the intensity and speed of training," Zoro said, panting as he collapsed to the ground. His chakra reserves were depleted—he couldn't keep climbing trees any longer.
Still, he was satisfied with his progress. Chakra had real benefits.
Circulating chakra through his body improved his speed and strength. He could feel it in every muscle.
As his control improved, so did his power. It was undeniable.
What he really wanted now was some high-intensity physical training. But this tiny ship didn't have enough space.
There were no wide-open areas, no terrain to test his blade.
For now, he was stuck with climbing trees and refining chakra.
Naruto, however, had a different solution.
"The answer is genjutsu," he said, his eyes gleaming. "I can cast an illusion that lets you fight powerful enemies inside a controlled mental world."
"Real combat is the fastest way to grow stronger."
"The more experience you gain—even simulated experience—the better your real-world combat effectiveness will be."
"And inside an illusion, time flows differently. You can train for hours or even days in the span of a few minutes."
"Once you accumulate the experience, it'll carry over into reality."
Naruto flashed a fox-like grin.
Zoro and Luffy both looked surprised.
"Genjutsu? There's no point in fighting fake enemies," Zoro said, crossing his arms with skepticism.
"Even if it's an illusion," Naruto replied, "it's no joke."
"If you don't take it seriously, it will hurt."
He wasn't exaggerating. Think of Tsukuyomi—the ultimate genjutsu that traps someone in a mental world where they're tortured endlessly for what feels like days. The pain is real. When the victim returns to reality, their spirit is shattered, their will broken.
Used correctly, genjutsu could be indistinguishable from reality.
And Naruto was no ordinary shinobi. As someone who had long transcended basic ninjutsu and seen through its essence, he could wield illusion with incredible precision.
He could construct entire mental worlds—vast, detailed, immersive.
He could even recreate people from memory, setting up enemies that his companions could face again and again.
A battlefield born of chakra and illusion.
A place to grow through trial and fire—without risking their lives.
Yes, this was going to work.
...
TN:
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