Chapter 8: Tempered a Thousand Times
Seven months later, the once scrawny Asuka had grown visibly sturdier. His frame had filled out, and he'd gained a noticeable bit of height.
His sword swings—once stiff and clumsy—had become fluid and sharp. Every cut now carried a keen whistle of wind.
Though he was still far from the storm-tearing power Arasaki had once demonstrated, the strength and stability behind his strikes were worlds apart from before.
The following day, as instructed, Asuka arrived at the foot of Hayama's most treacherous peak.
"The wind has no shape, no substance—gathering and dispersing without warning!"
"Don't think about resisting it. Feel its flow. Feel its power!"
"Merge with it! A swordsman of the Breath of Wind must not fear the wind!"
"Be as free as the wind, as all-pervading as the wind—
and like the wind… destroy everything!"
Here, the wind was even more violent—like invisible giant hands tearing at the body. One misstep, and a person could be swept straight off the cliff.
"Your foundation is solid," Arasaki said gravely.
"It's time to begin training Total Concentration Breathing."
"Strengthen the breathing method I taught you. Expand your lungs. Drive oxygen into every blood vessel, accelerate circulation and the heartbeat!"
"When you do, your body temperature will rise sharply. Bones and muscles will burn—allowing a human body to gain power comparable to a demon's!"
Standing at the base of the peak, Arasaki Tetsushin gave his orders.
"Asuka—starting today, you will climb to the summit barehanded every day."
"Once there, you will practice Total Concentration Breathing and your basic sword forms. Then you will climb back down."
"When you can complete all of this within two hours, come find me."
"Train with the resolve to die."
With that, Arasaki Tetsushin left—no further explanation given.
He believed that even alone, the fire in this boy's heart would be enough to drive him onward.
---
At first, the greatest challenge was climbing the mountain in the raging wind.
A sudden gust could fling him into the ravine below, smashing him into pulp—but after slowly familiarizing himself with the mountain paths, this became the simplest part.
The true trial lay at the summit.
There, gale-force winds poured straight into his mouth and nose. The thin air made breathing itself difficult—let alone maintaining Total Concentration Breathing.
His body swayed violently. Each sword swing became a struggle, his movements badly distorted.
Yet he didn't retreat.
Instead, he faced the wind head-on—breathing deeper, sinking further into the rhythm, refining his balance and point of exertion with obsessive precision.
He struggled within the storm like a lone wolf battling the elements—
blown off balance again and again, only to steady himself and swing the wooden sword once more, carrying an unyielding will.
The time required for his training steadily shortened.
Until one day, he could complete the entire routine in just over an hour.
After months of this, Asuka's skin had grown dark and rough from the mountain winds—but his eyes had only grown sharper, like a blade honed by frost and sand.
His footing atop the summit became increasingly stable. His sword swings, even in violent winds, began to flow smoothly—and he could faintly use the wind itself to adjust the angles of his attacks.
When he next appeared before Arasaki Tetsushin, the old man didn't even bother testing him personally.
Instead, he led Asuka to the back mountain of Hayama—to a secluded training ground.
Ancient trees towered overhead, branches thick and interwoven. Light barely reached the ground. The place was quiet—and dangerous.
For the next year, aside from Rika, who came and went daily, and Arasaki Tetsushin, who occasionally emerged from the back mountain to instruct other disciples—
No one saw Asuka again.
To Asuka, the four seasons of Hayama blurred away, leaving only the winds of the training ground:
The gentle spring breeze carrying the scent of new buds.
The scorching, dry winds of summer.
The bleak autumn gusts that swept fallen leaves away.
And the winter wind—razor-sharp, biting to the bone.
Asuka's body was already covered in scars.
Bruises from wooden-sword sparring.
Cuts from jagged rocks while climbing.
Scratches from branches while moving through dense forest.
And countless bandages from tendons—or even bones—damaged by forcing himself past his limits.
Old wounds hadn't yet faded—
when new ones layered over them once more.
Those marks covering his body were proof of a life spent desperately chasing power.
Time flowed on.
Cold gave way to heat, heat returned to cold.
By now, Asuka had spent a full two years in Hayama—the land that carried the legacy of the Breath of Wind.
Under Arasaki's guidance—harsh to the point of cruelty—Asuka's physical limits were pushed to the very edge of what a human body could endure. His once-fragile frame was now wrapped in dense, resilient muscle. Every line of his body flowed smoothly, brimming with explosive strength, each inch seeming to store the power of the wind itself.
More importantly, he had finally begun the systematic study of Breath of Wind sword forms.
From First Form through Ninth Form, Arasaki personally demonstrated their applications and the principles behind them.
Asuka learned quickly.
His body's instincts seemed innately attuned to the wildness and volatility of the wind. Though his power was still lacking, he had already grasped the essential rhythm and intent of the forms. What remained was tempering—endless repetition and refinement.
His swordplay lacked Arasaki's seamless, master-level composure. Instead, it carried a raw, feral quality—brimming with untamed vitality, like a sudden gale tearing across the wilderness without reason or restraint.
Beyond that, Arasaki noticed something else.
Whenever Asuka fully immersed himself in the forms of the Breath of Wind, there was always a faint, elusive pressure about him—as though some other force lay coiled within, ready to erupt at any moment.
"…A natural Breath used for demon slaying?"
Arasaki wasn't certain.
And yet—no matter how much Asuka's body strengthened, no matter how refined his swordsmanship became—the light in his eyes never truly changed.
When facing Arasaki or Rika, who had always looked after him with quiet kindness, that gaze softened slightly, carrying an almost clumsy sense of trust.
But at all other times—
His eyes were cold.
Distant.
Like a fierce beast temporarily given shelter—fed, sharpened, and allowed to grow strong—yet never once letting down its guard against the world.
Arasaki saw all of this clearly.
He had walked the edge between life and death countless times. He had taught disciples of every kind. He understood all too well that great power, if not guided by an equally strong state of mind, could easily slip into a dangerous abyss.
Often, in the quiet depths of Hayama's back mountain, Arasaki would watch Asuka train alone, sword rising and falling in silence.
He knew himself well enough to admit that he wasn't skilled in gentle guidance or emotional comfort. What he could give Asuka was only the strictest training, the firmest foundations, and demands bordering on the merciless.
He believed in this creed:
A great disciple is forged by a strict master.
Steel is made only through a thousand hammerings.
And yet—
This boy reminded him of another student.
Compared to that child, Asuka had nothing—not even a final bond or someone left to protect. That made him all the more worrying.
"Was my choice wrong…?"
Arasaki would sometimes ask himself.
"Have I focused too much on tempering his body, while neglecting the emptiness in his heart?"
"If he gains even greater power like this… will he lose his way instead?"
The thought lingered like a thorn, buried deep in the old man's chest, refusing to fade.
Until one day not long after—
The quiet of Hayama was shattered by a set of familiar, heavy footsteps—rough, impatient, and forceful.
The newcomer was tall and powerfully built, dressed in the Demon Slayer Corps' deep-green uniform. A white haori hung loosely over his shoulders, thrown on without care. Across its back, a single enormous character was painted in thick, savage ink:
「KILL」
As though all demons would be crushed beneath that overwhelming intent.
His short silver-white hair bristled with defiance. Several deep scars crossed his face—most striking of all, a long one slashing diagonally from forehead to cheek, adding to his ferocity.
But what drew the eye most were his eyes—
Sharp as a predator's.
They burned with barely restrained battle lust and naked aggression, as if he might tear into prey at any moment.
An invisible pressure radiated from his body, heavy enough to suffocate.
It was the terrifying presence forged only by standing at the brink of death time and time again—
by bathing in demon blood.
The current Wind Hashira of the Demon Slayer Corps—
Shinazugawa Sanemi.