Konoha, Training Ground 4.
The once-open woodland edge was now a disaster zone.
Trees thick as bowls lay snapped and scattered, fresh white splinters exposed at every break. The solid ground was pockmarked with craters and deep, crisscrossing trenches, as if some colossal beast had trampled it for days.
BOOM! BANG! THUD!
Heavy, drum-like impacts rolled across the field, each one shaking the earth and spraying dirt and stone.
Two figures moved at speeds the naked eye could barely track—blurring, colliding, separating, then crashing together even harder.
One silhouette was lightning-fast and agile, yet every direct clash sent it reeling backward under overwhelming force.
The other was built like a living mountain. Every step carried crushing weight, as if the body weren't flesh and blood at all, but forged from solid steel.
Another raw, no-frills punch!
THUD!
The shockwave detonated. The smaller figure—Shinichi Higashino—shot backward like a cannonball. He slammed into a massive tree that would take two men to hug. The trunk groaned, then snapped with a deafening crack.
Wood chips exploded everywhere. Shinichi let out a muffled grunt, using the falling tree as a cushion to flip and land. His feet carved two long furrows through the dirt before he finally stopped. His chest heaved, blood and chakra roiling inside him, both arms burning with numbness.
His training uniform was soaked with sweat and dirt, clinging to every swollen muscle. Rips and tears revealed skin covered in fresh bruises and flushed red.
Yet his eyes burned brighter than ever. They stayed locked on the massive silhouette slowly emerging from the swirling dust ahead. His breathing was heavy, but filled with near-maniacal focus.
The dust thinned.
A towering figure easily two and a half meters tall stood revealed.
It wore Konoha's forehead protector squarely on its brow, but it was no human.
Thick, steel-hard silver-white fur covered its body, gleaming with a cold metallic sheen under the sunlight filtering through the trees.
Every muscle bulged like carved granite—raw, explosive, radiating primal power that made the heart skip.
Its round golden eyes were pure wildness—sharp, fierce, ancient. Slightly parted lips revealed gleaming fangs.
Just standing there, it gave off the oppressive aura of a beast from the age of legends.
This was the Third Hokage Sarutobi Hiruzen's personal summoning beast—the legendary Ape Demon King, famed across the shinobi world for its unmatched strength and diamond-hard body.
When Shinichi had told the Third Hokage he wanted to train under a senior with an abnormally powerful and nearly indestructible physique, the old man had immediately thought of his longtime partner.
The Ape Demon clan was born with tyrannical physical power. Their bones and muscles far surpassed human limits. They didn't even need chakra to shatter boulders or split the earth with a casual swing.
Their muscle density and bone strength were simply insane—blunt-force impacts were naturally dispersed, ordinary blades barely scratched them. They were walking fortresses of living steel.
And so, the Ape Demon King had become Shinichi's personal trainer for this special session.
At their first meeting, the Ape Demon King had been blunt: the Ape Demon clan had no fancy, mysterious training methods. Their way of tempering the body was simple and brutal.
Fight. Take hits. Feel the impact. Endure the pain. Push past every limit until every muscle fiber and bone was reforged in the furnace of combat.
After each brutal session came their clan's secret medicinal baths and ointments—accelerating recovery, repairing hidden damage, and locking in the gains so the body could grow stronger through repeated destruction and rebirth.
In short: get beaten half to death, then heal.
The short lull in the center of the field gave Shinichi a moment to steady his breathing. He felt the burning ache in his arms and the white-hot fire running through his muscles.
The Ape Demon King followed the simplest creed of his kind: only when pushed to the absolute brink—or beyond—could flesh and blood truly evolve.
His training style was merciless: as long as it didn't kill you, it wasn't hard enough.
This kind of sparring had been going on for days. Every evening Shinichi ended training covered head to toe in bruises, skin barely intact anywhere, bones feeling like they were about to fall apart.
Luckily, the Ape Demon King's secret medicines were miraculous. Combined with Shinichi's already superhuman constitution and the [Glutton King] trait that let him absorb nutrients and convert energy at terrifying efficiency, he was able to endure the insane daily grind.
"Kid! Pay attention!"
The Ape Demon King's voice boomed like a bronze bell, carrying a metallic edge. The moment the words left his mouth, his massive body dropped into a low crouch, legs tensing with power that made the ground crack.
BOOM!
The earth beneath his feet collapsed into a crater as the Ape Demon King launched himself skyward. His enormous frame moved with shocking speed and explosive force that completely defied his size.
Like a meteor falling from the heavens, he fused his terrifying weight with the momentum of descent into the most primal, violent attack imaginable—smashing straight down toward Shinichi!
Shadow swallowed everything. The wind howled. The very air screamed as it was violently displaced!
Can't take this head-on!
The instant the Ape Demon King jumped, Shinichi reacted. He didn't retreat or dodge sideways—the attack's range was too wide.
Instead, he charged forward, straight into the dead zone beneath the ape, dropping his body so low he was almost skimming the ground like a black lightning bolt.
WHOOSH!
At the last possible moment, Shinichi slipped through the edge of the landing zone by a hair's breadth. The savage wind pressure nearly yanked him off his feet and scraped his exposed skin raw.
BOOOOOOM!!!
The Ape Demon King crashed down like a falling star. The impact point became the center of a violent shockwave that rippled outward in a perfect ring. The hard ground buckled like water, then exploded.
Countless stones and chunks of earth were hurled into the air, carving out a terrifying crater over ten meters wide.
Shinichi didn't pause for even a heartbeat. The moment he escaped the killing blow, his counterattack ignited. Using the flying sand and debris as cover, he spun violently, twisting his waist and pouring every ounce of strength and chakra into his right leg. A vicious side kick—sharp as a battle-axe—whipped toward the Ape Demon King's ankle joint right after landing, the spot least able to generate power!
BANG!
Leg bone met ankle. The sound was like kicking a solid steel pillar.
The Ape Demon King's body only swayed slightly. He didn't move half a step.
"Not bad power, but still lacking!" the Ape Demon King rumbled. His massive arm swept out casually, like a falling tree trunk, carrying unstoppable force.
Shinichi yanked his leg back and crossed both arms in front of his chest.
THUD!
Arms collided with the ape's forearm. Shinichi felt like he'd been hit head-on by a charging tank at full speed. Both blocking arms went instantly numb. His entire body was sent sliding backward uncontrollably, feet carving deep trenches in the ground as he flew more than ten meters before finally bleeding off most of the impact.
---
"Hey, kid!"
The Ape Demon King didn't press the attack. He stood with arms crossed, golden eyes calmly appraising Shinichi, who was still catching his breath more than ten meters away.
"From now on, you can use ninjutsu."
Shinichi blinked. For nearly a month of hellish training, both sides had stripped away every flourish, clashing with nothing but the purest taijutsu, raw strength, and endurance.
The Ape Demon King had been clear: only after the body truly remembered the essence of power could they move on to anything else.
And through these no-holds-barred sessions, he had personally witnessed just how monstrous this boy's physique truly was.
That terrifying strength, recovery speed, and pain tolerance… it didn't seem human at all.
If the Third Hokage hadn't already told him the kid was a civilian orphan, the Ape Demon King would have suspected some unknown bloodline limit or a connection to the Senju clan, famous for their legendary bodies.
"You want to create your own taijutsu-ninjutsu fusion, right?" Seeing Shinichi's expression, the ape explained in his deep, metallic voice. "I don't have any fancy ninjutsu techniques to teach you. Hand seals and jutsu aren't the way of my clan."
He paused, then continued, "But combining existing power, making taijutsu and ninjutsu flow together in actual combat until they stop being separate things and become as natural as breathing… that kind of integration can only be forced out under real pressure."
His meaning was clear: in the next phase of training, Shinichi could freely use any ninjutsu he knew.
The goal was no longer just to endure or dodge. Under the crushing pressure the Ape Demon King provided, Shinichi was to try weaving ninjutsu release, control, and setup with taijutsu movement, entry, and explosion timing—searching for that seamless, unified feeling. It would lay the raw, practical foundation for the "ninja body technique" he dreamed of creating.
"Come on," the Ape Demon King's voice dropped low, filled with absolute confidence. "Attack me with the intent to kill. Don't worry about hurting me. In the current shinobi world, there is nothing that can truly injure me."
---
Some time later.
The training ground was even more devastated than before—scorched black marks from Fire Release and fresh craters everywhere, clear signs the fight had entered a new stage.
A piercing, high-pitched energy hum cut through the air as Shinichi seized a fleeting opening and drove the head-sized azure chakra sphere straight at the Ape Demon King.
Rasengan!
The Ape Demon King reacted instantly. At the last possible moment he raised his right palm and met the madly spinning, terrifyingly penetrative orb head-on.
The Rasengan carried not only razor-sharp piercing force but also a condensed, crushing weight.
Under the impact, even the Ape Demon King's mountain-like body couldn't stay completely still. He slid backward, both feet digging deep trenches into the ground, stopping only after seven or eight meters.
Dust drifted upward.
The Ape Demon King lifted his gaze to the black-haired boy panting heavily in the distance, clearly exhausted from the massive output. Then his eyes dropped to his own right palm—the one that had blocked the Rasengan.
The tough, blade-resistant fur in his palm had been torn away in a large patch. The tough skin beneath was split open, and a thin line of bright red blood was slowly seeping out.
He stared at the blood in silence.
"Ape Demon King, sir… are you alright?" Shinichi asked, still catching his breath.
In the fight just now, he had gone all-out—layering multiple ninjutsu to create openings—finally earning this close-range chance to force the Ape Demon King to take a full-power Rasengan head-on.
Although the Ape Demon King was famed for his "diamond-hard" body, it wasn't literally indestructible. In the original timeline, his palm had once been cut by Orochimaru's Kusanagi Sword.
Speaking of "diamond-hard," that was another unique talent of the Ape Demon clan—shape transformation.
They could completely weaponize their bodies according to battle needs, freely transforming into the form known as the "Adamantine Staff."
In that unique weapon form, their hardness and strength underwent a qualitative leap.
Not only could they clash head-on with divine blades like the Kusanagi Sword without taking damage, they could even knock the rampaging Nine-Tails flying out of Konoha with a single swing.
Even during the Fourth Great Ninja War, the Third Hokage had used the Ape Demon King in this form to shatter the Ten-Tails' dense Wood Release barrage and save Naruto Uzumaki.
Perhaps only in that "Adamantine Staff" form did the Ape Demon King truly deserve the title "diamond-hard."
In his regular ape form, "steel bones and iron muscles" was a more accurate description.
In that state, he could ignore the vast majority of ordinary ninjutsu and taijutsu strikes. His defense was terrifying.
However, against truly powerful techniques—or divine weapons like the Kusanagi Sword—his powerful body could still be broken and wounded.
"Very good…" The Ape Demon King's deep voice broke the silence. He shook his hand, flinging drops of blood onto the ground. "Not bad at all."
Perhaps embarrassed that his earlier claim of being "impossible to injure" had been proven wrong, his tone carried a hint of awkwardness.
"We'll end today's training here," the Ape Demon King said.
Before Shinichi could respond, the massive body suddenly burst into a thick cloud of white smoke with a loud poof and vanished on the spot.
In the center of the devastated training ground, only a more ruined landscape remained—toppled trees, scattered craters, and… at the exact spot where the Ape Demon King had stood, a few drops of dark red blood that had yet to fully soak into the dirt and gravel stood out starkly.
Shinichi's gaze lingered on those bloodstains for a moment, his eyes flickering.
But he didn't do anything else. Just like after every previous high-intensity session, he let out a long, exhausted, scorching breath,
then silently began cleaning up the mess—gathering broken wood, roughly filling in the most obvious craters. Everything looked exactly the same as usual.
---
One month later, southern border of the Land of Iron, Forging Iron Town.
This border town, which shared a boundary with the Land of Fire, was famous for its mining and blacksmithing industries. The air always carried a faint metallic and charcoal scent.
Inside a tavern called "Sakura View Pavilion," business was booming.
The noren curtain hung low, unable to block the rising steam and clamor inside.
Rough clay cups clinked together. People in various traveler's clothes or work aprons sat around low tables—mostly ronin, merchants, and local craftsmen. The air was thick with the salty aroma of sake, grilled fish, and soy sauce.
They talked about recent ore prices, stories from border patrols, or which workshop had just landed a huge order.
Rough laughter and bragging rose and fell in waves.
Then the tavern's thick wooden door creaked open, letting in a gust of cold outside air.
A tall figure stood silhouetted in the doorway. After a brief moment of silence, a clear, bright voice—full of undisguised eagerness and unshakable confidence—cut through the noise and reached every ear in the room:
"Excuse me, everyone."
"Who hits the hardest in Forging Iron Town?"