The night was deep.
Uesugi Sasuke lay with his eyes open, not the least bit sleepy.
From the room next door, Zenitsu Agatsuma's steady snores and occasional sleep talk pricked his nerves like tiny needles.
The scene from that day replayed over and over in his mind.
That faint, fleeting flash of electricity.
That fragment of Thunder Breathing, performed unconsciously in his sleep.
Why?
Sasuke could not understand.
A cowardly, weak-willed good-for-nothing who did nothing every day but cry and run away.
Why did he get to have the talent I dreamed of?
And he, Uesugi Sasuke, was a genius chosen by the system, possessing an advanced power system from another world.
Yet he met with failure at every turn before this towering wall called a "Breathing Style."
That feeling was harder for him to bear than any physical pain.
It was a sense of injustice and displacement that came from deep within his soul.
The next day.
Dawn had barely broken.
Jigoro Kuwajima summoned both disciples to the training hall.
The old man's expression was unusually stern.
"Starting today, I will formally teach you the mysteries of Thunder Breathing."
Terror instantly filled Zenitsu's face.
Sasuke's gaze sharpened as he focused all his attention.
"The foundation of any Breathing Style lies in Total Concentration Breathing."
Kuwajima's voice was low and powerful, echoing through the empty training hall.
"Flood your blood with vast amounts of oxygen in an instant, activate every cell, and let your bodies unleash strength beyond human limits for a short time."
"This is the only way you can fight demons with mortal bodies."
He paused, his gaze sweeping over his two disciples.
"Thunder Breathing has six sword forms. But every one of them originates from the First Form."
"First Form, Thunderclap and Flash."
Kuwajima drew his Nichirin Blade. Though he had only one leg, his stance was as steady as a mountain.
"Watch closely."
He made no unnecessary movements, simply sheathing his sword slowly and lowering his body slightly into the opening stance of a quick-draw slash.
"Thunder Breathing is about ultimate speed and explosive power. In a single breath, concentrate all the strength in your bodies into your legs."
"Then tear through the air like real lightning."
The instant his words fell, Kuwajima vanished.
No.
He had not vanished.
Sasuke's pupils contracted sharply.
He could see it clearly.
The old man's figure became a streak of yellow electricity, crossing more than ten meters in an instant at a speed almost impossible to follow with the naked eye and appearing at the other end of the training hall.
He still held his sword-sheathing pose, as though he had never moved.
"That is Thunderclap and Flash."
Kuwajima's voice came from the distance.
Zenitsu's mouth had fallen open in fright, leaving him speechless.
A storm of shock surged through Sasuke's heart as well.
So fast!
That speed had completely surpassed his understanding of Taijutsu.
"Give it a try," Kuwajima said, slowly walking back.
Sasuke took a deep breath and closed his eyes, rather than immediately copying the movements.
Instead, he began to analyze them.
He recalled the flow of blood inside Kuwajima's body, the contractions of his muscles, and the way his bones exerted force.
He tried to deconstruct the move with his genius mind.
Then he moved.
He assumed exactly the same stance as Kuwajima, matching every detail without the slightest deviation.
He controlled his breathing, ordering his muscles to exert force in the sequence he had analyzed.
"Thunder Breathing, First Form..."
With a low shout, he took a sharp step forward.
Whoosh!
He did charge forward, considerably faster than an ordinary run.
But that was all.
There was none of that lightning-fast sensation of tearing through the air.
It was more like a sprint with too much force behind it.
"Idiot!"
Kuwajima's cane struck his back without mercy.
"What are you doing? Are you trying to cut people with your brain?"
"Your body is stiff! Your breathing is a mess! I told you to become lightning, not to think about how to become lightning!"
Sasuke stiffened, a trace of astonishment and defiance flashing through his eyes.
He had clearly copied every detail to perfection.
"Again!"
Refusing to accept it, Sasuke tried again.
The result was still the same.
No matter how precisely he controlled his body, he could not produce that instantaneous burst of speed.
It was as though a sheet of paper separated his strength from his body, one he could never pierce.
"You!"
Kuwajima seemed to lose patience with him and turned to point at Zenitsu, who was trembling beside them.
"You useless fool! Show him how it's done!"
"Me? I can't, Master!"
Zenitsu's tears immediately spilled over.
"I'll die! I really can't do it!"
"You little bastard! Do as you're told!"
Furious, Kuwajima kicked Zenitsu in the backside.
Zenitsu stumbled forward from the kick and cried even harder.
Just then.
Rumble-!
A dull clap of thunder came from the distant sky.
The weather on Mount Momoyama was always this changeable.
"Aaaaaah! Thunder!!"
Hearing the thunder, Zenitsu shrieked like a cat whose tail had been stepped on, rolled his eyes back, and actually toppled straight backward.
He had fainted from fright.
Kuwajima sighed helplessly and was just about to say something.
Something strange happened.
The blond boy lying unconscious on the floor suddenly began twitching involuntarily.
A stream of scorching white vapor burst from his nose and mouth.
Then his limp body actually began moving on its own.
It adjusted itself in an extremely bizarre posture, assuming the preparatory stance for Thunderclap and Flash.
His knees bent slightly, his center of gravity lowered, and his hand settled on the wooden sword at his waist.
Sasuke's eyes widened instantly.
"Thunder Breathing..."
A barely audible murmur escaped Zenitsu's lips in his sleep.
The next instant.
Whoosh!
A faint streak of electricity flashed.
Like a phantom, Zenitsu vanished from where he stood.
When he appeared again, he was five meters away.
He still held his sword-drawing pose, then went limp and collapsed completely onto the floor, snoring loudly.
The entire training hall was so quiet that a falling pin could have been heard.
Sasuke stood frozen, as though struck by lightning.
What had I just seen?
What kind of speed was that?
Without any preparation, without deliberately exerting force, relying only on instinct while unconscious...
He had achieved the burst of speed that Sasuke could not reach despite all his agonizing thought and repeated attempts.
That was not imitation.
That was the true rhythm of thunder.
A fierce flame called jealousy, mingled with humiliation and resentment, burned wildly in his chest.
I lost.
For the first time, he had lost so completely to someone he despised from the bottom of his heart.
"Did you see that?"
At some point, Kuwajima had walked up beside him, his voice carrying complicated emotions.
"That is talent."
"That useless fool's body is far more honest than his brain. His body remembers the sound of thunder, remembers the rhythm of breathing. It's just that his cowardly mind keeps resisting all of it."
Kuwajima turned his head, fixing his single eye on Sasuke.
"You, on the other hand, are the exact opposite."
"Your will is as firm as steel, and your body is a perfect weapon. But your brain is too 'clever.'"
"You keep trying to analyze, calculate, and control. You want to harness thunder with your will."
"But you're wrong, Sasuke."
"Before you learn to harness thunder, you must first learn to listen to its voice."
Listen?
Sasuke fell silent.
He did not understand.
In his world, there was only conquering or being conquered.
Late that night.
Alone in the courtyard, Sasuke mechanically repeated his sword swings.
As the wooden sword sliced through the air, it made only the hollow sound of wind.
Not thunder.
His mind was filled with Zenitsu's phantomlike flash and Kuwajima's words, "Learn to listen."
His pride, his confidence as a genius, was shattered at that moment.
Confusion enveloped him like a vast net.
A long time passed.
He stopped moving and gripped the wooden sword tightly.
An unprecedented obsession and madness churned in his pitch-black eyes.
Listen?
What if I can't hear it?
Then I'll use my own methods to force thunder to make the sound I want.
Before you continue