"Listen up, brat!" Tsunade said, clapping her hands together as if she'd just touched something unpleasant.
"You said you want to learn medical ninjutsu from me, right? Then follow me."
"How much you can actually learn—"
"that depends entirely on you."
"Thank you, Tsunade—neechan."
The instant the word left his mouth, Tsunade's fist twitched upward.
"…Tsunade-sensei," Kirito corrected himself immediately.
"Hmph."
Seeing Tsunade finally agree, Jiraiya came running over from afar, not even bothering to brush off the dirt on his clothes.
"Hahaha! That's great! I'll leave Kirito to you, Tsunade!"
"As for me—this place is perfect, so I'll be heading off to… collect materials!"
With lewd laughter echoing behind him, Jiraiya vanished in a flash, disappearing from the courtyard before anyone could stop him.
"…That bastard," Tsunade muttered.
She turned back to Kirito, arms crossed.
"Brat, just because you've become my disciple doesn't mean you can rely on me for everything. I—"
"I understand, Tsunade-sensei."
Kirito interrupted calmly.
Tsunade stared at his indifferent face.
A vein slowly surfaced on her smooth forehead.
"…What an arrogant little monster."
"We start formal training tomorrow," she said sharply.
"Rest early tonight."
"Shizune, let's go."
"Yes, Tsunade-sama."
Shizune gave Kirito an apologetic look before following Tsunade out of the courtyard.
The gate closed.
Silence returned.
Kirito didn't chase after them.
Instead, he reached into his clothes and took out a scroll.
This was the scroll Jiraiya had given him.
Inside was a single ninjutsu—
The signature technique of the Fourth Hokage.
Rasengan.
Strictly speaking, Kirito was far too young to train this technique properly.
But Jiraiya wandered constantly, and Tsunade lived like a drifting cloud.
No one knew when the next meeting would be.
So Jiraiya had entrusted it to him early.
While refining chakra on the ship, Kirito had already formed a hypothesis.
During the Nine-Tails Rebellion, it should have been impossible for him to use the Dark Fruit to seal Minato and Kushina into the darkness.
At that time, his physical stamina had been completely exhausted.
What sustained the Dark Fruit's activation—
Was chakra.
If chakra could truly merge with Devil Fruit abilities…
Not only would the power increase drastically—
The upper limit of his overall strength would rise as well.
And Rasengan—
A no-hand-seal, non-elemental ninjutsu—
Was the perfect experimental medium.
With that thought, Kirito began studying the scroll.
The private courtyard was ideal—
isolated, quiet, and safe from prying eyes.
"First… darkness."
Kirito extended his left hand.
Wisps of black mist seeped out, curling slowly around his fingers.
His fight with Tsunade had confirmed something important.
The Dark Fruit—after being strengthened by the system—
was far beyond what it had been in the pirate world.
In a world without Devil Fruit users, he'd assumed its ability-absorption aspect would be meaningless.
But he was wrong.
This darkness could absorb chakra.
If further developed—
Enemy ninjutsu could be swallowed directly.
In terms of pure efficiency, it might even surpass Mangekyō techniques like Kamui.
And the Dark Fruit didn't just absorb.
It released.
What it swallowed could be expelled again.
Which meant—
Repulsion was also part of its authority.
Even if the original Dark Fruit never had such applications—
A system-enhanced version, with limitless development potential, would eventually command all concepts tied to gravity.
At that point—
He would truly stand at the top of this world.
Then there was the Tremor Fruit.
Kirito raised his right hand.
"Humm…"
A transparent white ring slowly formed.
In the pirate world, this power had been developed by Whitebeard to the point of world destruction.
Even Sengoku had acknowledged it as such.
And this version—
Enhanced by the system—
Was even more terrifying.
Not just vibration.
But secondary effects: tearing, slicing, spatial collapse.
It was no weaker than the Dark Fruit.
Which meant—
The so-called Peak Blackbeard Template wasn't a fixed ceiling.
It was merely a foundation.
After all, Kirito had never seen Blackbeard's true endpoint in his previous life.
But one thing was certain—
This system-enhanced template far exceeded anything Blackbeard himself had shown.
And then there was Conqueror's Haki.
What kind of effect would that have once fully developed?
A trace of heat appeared in Kirito's eyes.
In his previous life, power-scaling arguments never ended.
But one truth remained constant—
If an ability was strengthened without limit, even the simplest power could reach the absolute peak.
And these weren't simple abilities.
They were the top-tier powers of the pirate world.
If developed properly—
Nothing in this world would be able to stop him.
Kirito dispersed both abilities and focused inward.
He mobilized his chakra.
Anyone who had watched the anime knew Rasengan's training process.
At its core—
Chakra control.
Naruto's initial failure hadn't been due to poor control.
It was because the Nine-Tails' chakra constantly interfered.
Sealing techniques themselves demanded extreme chakra precision.
There was no way the Uzumaki clan—
masters of sealing and possessors of a Sage-level body—
lacked chakra control.
Kirito carefully guided the chakra's flow.
Under the influence of Dark Fruit gravity, his control grew even sharper.
He spread his right hand.
A chakra sphere—
no larger than half a finger—
formed in his palm.
Boom!
It shattered seconds later.
"…Too little chakra?"
Kirito exhaled and tried again.
This time, the chakra sphere ballooned—
nearly the size of a basketball.
But it was unstable.
Distorted.
Twisting wildly.
Boom!
Another failure.
And so he continued.
Boom.
Boom.
Boom.
…
Time slipped by.
Each time his chakra dried up, he sat down—
letting the Uzumaki body's terrifying recovery replenish him...
then resumed.
From noon.
Until sunset.
Kirito never stopped.
Finally...
"Humm…"
A palm-sized, perfectly condensed sphere of blue chakra spun steadily in his hand.
Rasengan.
Success.
Yet—
Kirito felt no excitement.
Because this was only the most basic form.
If he wanted to add elemental transformation—
like Naruto would one day—
There was still a very long road ahead.
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