Mount Myōboku.
Jagged peaks and grotesque rock formations rose amid an endless forest of colossal mushrooms, all shrouded in a faint, seven-colored mist.
Anyone with discernment would immediately realize—
This mist was natural energy, so dense it was nearly liquefying.
From afar came the low thunder of waterfalls, interwoven with constant croaking.
Near one such waterfall, several basin-sized green toads lounged lazily, basking in the sunlight.
Buzz.
A golden pillar of light suddenly tore through space.
A small figure stumbled out of it, landing awkwardly.
Step—step—step.
Kai staggered before finally steadying himself atop a slick stone platform.
The commotion instantly drew the attention of the nearby toads.
"Waaah! This toad is so ugly! No bumps on its back at all!"
"That's not a toad, idiot—that's a human! A real human!"
"A human? Did Jiraiya-sama take in a new disciple?"
"What disciple?! Humans are humans—proper, upright humans!"
They crowded together, chattering noisily—
and then promptly started fighting over whether Kai was a human or a disciple.
Kai: "..."
So… the toads of Mount Myōboku were this lively, huh.
He twitched the corner of his mouth and looked around.
Immortal mist drifted through the air, frogs croaked from every direction.
This was Mount Myōboku.
The sacred land of senjutsu.
Perhaps the oldest birthplace of sage arts in existence.
Kai's expression turned complicated—part curiosity, part awe, part quiet surprise.
It wasn't quite how he had imagined it…
and yet, somehow, it was exactly as it should be.
This was Mount Myōboku.
After a brief pause, he took a deep breath.
Boom!
Just that single inhale pulled in an overwhelming torrent of natural energy.
It seeped in through his lungs, pores, and bloodstream—
far heavier and more violent than chakra refined from body or spirit.
The moment Kai sensed it, he instinctively mobilized his chakra to balance it.
Even so—
His skin stiffened.
His limbs grew rigid.
Like… petrification.
The very first sign of failing to control senjutsu.
Just two breaths in, and he was already showing signs of turning to stone.
Kai frowned sharply, lowering his head to inspect himself.
Something felt off.
After that first breath, the natural energy didn't just disperse—it flowed downward with his blood and breath, converging somewhere below.
gurgle…
"This feeling is…"
He looked down.
His face darkened instantly.
Both feet had stiffened. Even his toes barely moved.
Stone transformation—no doubt about it.
He could feel the violent natural energy outside still pouring relentlessly into his body.
If not for his partial high-grade Wood Release cells and the overwhelming mental strength of the Mangekyō, he would've already been fully petrified.
"But…"
Kai was confused.
Wasn't the standard method to apply toad oil to the skin to sense natural energy first?
So what exactly was happening to him?
After a moment's hesitation, he casually planted a Flying Thunder God marker nearby.
Then—
He stopped resisting.
He fully opened his Mangekyō and released his Wood Release cells.
If he couldn't block it anyway, he might as well let it all in.
Crack.
Crack crack.
A series of sharp popping sounds echoed from within his body.
Under the savage wash of natural energy, Kai's body was undergoing a deep, violent transformation.
His cells were rejoicing—
and at the same time, being torn apart.
Painful.
Exhilarating.
Pain and pleasure intertwined.
"Hoh? An interesting little one."
A deep, aged yet energetic voice suddenly sounded nearby.
Kai turned his head.
At the edge of the platform, squatting atop a massive lotus leaf, was a small old toad wearing a blue vest and puffing calmly on a pipe.
His frog eyes—weathered by countless years—were now filled with disbelief.
Especially when he saw Kai absorbing natural energy simply by breathing.
Those eyes bulged so wide they nearly popped out.
All the wisdom and composure drained away, replaced by pure, stunned confusion.
"Th-this… this is impossible!"
"No toad oil, yet he can sense natural energy?!"
"Is this child a son of nature or something?!"
"Even that child from over ten years ago—Minato—needed to be soaked in oil for an entire month before sensing it!"
Deeply familiar with how difficult senjutsu truly was, the old toad knew just how absurd this scene was.
Even with a Sage personally guiding them, most humans needed enormous time and effort to take the first step.
Yet this boy—
On his first visit, just by staying a while, he had absorbed natural energy.
And absorbed too much, to the point of petrification!
It was ridiculous.
So ridiculous that—
The old toad's pipe slipped from his mouth and fell to the ground.
Goosebumps rippled across his back beneath his clothes.
"And… no visible toad contract mark, yet he used a complete reverse summoning…"
"And that chakra inside him… Wood Release? And the same spatial fluctuation as that Minato boy…"
Then his eyes caught sight of the Flying Thunder God formula Kai had planted.
They widened again.
At last, he thought he had figured it out.
"Boy… are you that child Minato's descendant?"
Kai: "…Me?"
He stared at the old toad, genuinely baffled.
How did that leap of logic happen?
Wasn't Minato blond?
Kai raised his head and smiled brightly, with a boyish sincerity.
"You must be Fukasaku-sama? I'm Uchiha Kai."
Gero!
Several small toads jumped away in shock at the name.
Even in Mount Myōboku, the name Uchiha carried weight.
"…Uchiha?"
"So… not Minato's bloodline…"
Fukasaku picked up his pipe and tapped it against the ground, eyes fixed firmly on Kai.
The caution he'd momentarily relaxed returned in full force.
"An Uchiha brat shouldn't be here on Mount Myōboku…"
"But, Fukasaku-sama," Kai scratched his head and grinned,
"since I'm already here…"
"Why not teach me senjutsu?"
Who knew—maybe talking to toads could copy traits too.
And as the father of the 'Mount Myōboku underworld boss,' Fukasaku's traits were bound to be extraordinary.
"You are not one chosen by fate. You must leave."
This time, Fukasaku neither debated nor explained.
He simply raised a small toad hand—
—and slammed it down.
Whoosh!
A thick, sticky, dark-brown substance materialized out of thin air.
Pungent.
Viscous.
Like a living brown serpent.
Like a monster sculpted from stone.
It crashed straight toward Kai.
It was an attack—
but also not an attack.
If Kai couldn't endure it, the flood of natural energy would overwhelm him, turning him into stone… or flinging him straight back out of Mount Myōboku.
But if he could endure—
Then this was the very first step of Mount Myōboku's senjutsu training.
Applying toad oil.
If he could absorb this much natural energy without oil—
Then what kind of monster would he become with it?
The thought made Fukasaku's heart stir with anticipation.
For the first time in many years—
He wondered whether Mount Myōboku's senjutsu…
might finally be pushed to its limit.
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