The moonlight was like frost.
Uesugi Sasuke stood alone in the empty courtyard, motionless.
The scene from that day burned through his mind over and over, like a brand that could not be erased.
That useless Zenitsu Agatsuma had used the Thunder Breathing Sasuke had failed to master despite all his practice, relying on instinct while unconscious.
That faint yet unmistakably real flash of electricity.
That speed that tore through the air.
Jigoro Kuwajima's words echoed in his ears.
"You must first learn to listen to the sound of thunder."
Listen?
A cold curve tugged at the corner of Sasuke's mouth.
What an irony.
He, Uesugi Sasuke, was a genius chosen by the system, a transmigrator who possessed a higher power system from another world.
And now he had to learn how to "listen" from a cowardly good-for-nothing?
No.
He refused.
He had his pride.
If he couldn't hear it, that proved this method was wrong, inefficient.
He would find the answer his own way.
He would conquer that flash of lightning in a way that belonged to Uesugi Sasuke.
He slowly closed his eyes.
The figures of Kuwajima and Zenitsu surfaced in his mind again.
This time, he did not try to feel some elusive "rhythm" or "pulse."
He put his far-above-average brain to work.
His Sharingan had yet to awaken, but his ability to analyze and deconstruct was still his strongest weapon.
First Form, Thunderclap and Flash.
The movements slowed down without limit.
Every contraction of muscle, every twist of bone, the entire process of power traveling from the soles to the waist and abdomen, then to the thighs.
He broke everything down into individual, quantifiable pieces of data.
There was no mystery, no mysticism.
In his eyes, it was merely a complicated physics problem concerning the explosive power of the human body.
All he had to do was use this body to reproduce every step perfectly and arrive at the final answer.
He opened his eyes, picked up the wooden sword beside him, and sheathed it.
He did not begin immediately.
Instead, he adjusted his stance over and over.
The angle of his bent legs, how far he lowered his body, the point of contact between his arm and the sword's hilt.
Like the most exacting craftsman carving a lifeless work of art, he pursued precision down to the millimeter.
Then he moved.
There was no guidance from a Breathing Style, nor any instantaneous burst of power.
He simply drove his muscles in the sequence he had worked out in his mind.
A step, a draw.
Whoosh!
The wind sounded, and nothing more.
It was a sword-drawing slash so textbook-perfect it could have been written into a manual.
It was fast.
But it was only fast.
It fell far short of the lightning speed Kuwajima had demonstrated.
Sasuke was not discouraged in the slightest. Expressionlessly, he sheathed his sword and repeated it.
Once.
Ten times.
A hundred times.
He devoted the entire night to this dull, mechanical repetition.
He knew no fatigue and felt no boredom.
Because this was his path, a road to the pinnacle through calculation and control.
Under the distant eaves, Jigoro Kuwajima watched quietly with a coat draped over his shoulders.
He did not speak up to stop him.
He saw Sasuke's movements.
That precision, that control, startled even him, a former Rumble Hashira.
But he also saw the problem.
This boy was too "clever."
He treated his body like a machine, using reason to issue its every command.
Movements produced that way were dead.
They had no soul, no life.
Much less the fury of thunder.
"Ah..."
Kuwajima let out a long sigh and turned back into the house.
He knew Sasuke could only run into this wall himself.
Only when he had battered himself bloody against it, only when he gave up thinking with that "clever" head of his, could he truly begin walking the path of a swordsman.
Dawn was just breaking.
Yawning and bleary-eyed, Zenitsu Agatsuma came out to use the toilet.
Then he saw that ghostlike figure beneath the moonlight.
Sasuke was still swinging his sword.
His clothes were already soaked with sweat, clinging tightly to his body.
His feet had stamped two shallow pits into the ground beneath him.
Every swing of his sword carried a crazed obsession.
Zenitsu shuddered in fright, all his sleepiness gone.
He had never seen anyone like this.
This junior fellow disciple seemed not to be human, but a fighting machine that felt neither fatigue nor pain.
"S-Sasuke..."
Zenitsu summoned his courage and called out softly.
"D-don't you need to sleep?"
Sasuke's movements did not pause in the slightest.
He did not even turn to glance at Zenitsu, merely forcing one cold word out of his throat.
"Scram."
Zenitsu nearly cried in fright. He scrambled back into his room and pulled the covers over his head.
Terrifying.
This junior fellow disciple was scarier than a demon.
Day after day passed in this strange atmosphere.
By day, Sasuke trained alongside Kuwajima and Zenitsu, his face expressionless.
At night, he began his own "research."
He discovered that simply imitating the movements had reached its limit.
It was because his body was not strong enough.
And so his training became even more brutal.
Weighted laps.
Single-leg squats.
Frog jumps.
He completed ten times the volume of every exercise that could develop explosive power in his legs.
His legs became as hard as steel.
His speed did indeed improve visibly.
When he sprinted at full speed, he was already a blurry black shadow to ordinary people's eyes.
But he still could not reach that realm.
The realm of "thunder."
His speed came from an explosive release of muscular strength.
But the speed of Thunderclap and Flash came from burning life force.
There was a fundamental difference between the two.
That night.
After yet another failed sprint, Sasuke finally stopped.
He stood in the middle of the courtyard, his chest heaving violently, sweat streaming down his face like little rivers.
Why?
He had already analyzed the movements to the utmost.
He had already trained his body to its limit.
Why was it still not working?
What exactly was that final piece, that qualitative leap from "fast" to "lightning"?
Intense frustration and unwillingness burned in his chest.
"Damn it!"
With a low snarl, he hurled the wooden sword in his hand.
Crack!
The wooden sword struck a distant peach tree and snapped.
Drained of strength, Sasuke sank to his knees and pounded the ground with his fists.
For the first time since coming to this world, he felt such profound helplessness.
Not the helplessness of facing a powerful enemy.
But an intellectual helplessness, facing an invisible wall he could not cross even after exhausting every method.
The "talent" he took the most pride in had become a joke here.
A long time passed.
He raised his head and opened his right hand.
The savage lightning of Chidori seemed to linger in his palm.
That was his power.
A power he could control perfectly and perceive clearly.
Wait...
Power?
A thought split the fog in his mind like a real bolt of lightning.
Had he... gotten it wrong again?
Was a Breathing Style really a kind of "power"?
No.
Kuwajima had said Breathing Styles allowed the body to surpass its limits and thus unleash greater power.
So a Breathing Style itself was not the source of power.
It was a kind of... switch.
It was a "technique" that overclocked the performance of the machine that was the body to its limit!
His body was different from those of the people in this world.
Besides blood, another, higher, purer form of energy flowed through his body.
Chakra.
If the people of this world used the "switch" of Breathing Styles to squeeze 120% out of their bodies' potential...
Then what about him?
Could he use this "switch" to ignite the volcano within him called "chakra"?
Not make chakra adapt to a Breathing Style.
But instead, make a Breathing Style become the... trigger for his Ninjutsu!
Once this idea appeared, it could no longer be contained.
Sasuke sprang to his feet.
The humiliation of failure, the bitter unwillingness of helplessness, all turned at that moment into an almost crazed exhilaration.
He had found it.
He had found that unique path that truly belonged to him alone.
He walked beneath the tree, picked up the broken half of the wooden sword, and gripped it tightly.
An unprecedented light surged in his pitch-black eyes.
First Form, Thunderclap and Flash.
If my body didn't have enough fuel.
Then let me stoke it with an even greater fire.
Before you continue