Seven months later, the once-skinny Asuka had begun to grow sturdy, his height shooting up as well.
His sword swings, which had initially been stiff and clumsy, had become smooth and fierce. Each strike now carried a sharp whistle of wind.
Though he was still far from reaching the storm-rending power Arasaki had once demonstrated, the sense of strength and stability behind his blows was no longer comparable to before.
The next day, following Arasaki's instructions, Asuka arrived at the foot of the most perilous peak of Hayama.
"Wind has no form or substance. It gathers and scatters without constancy! Don't think about resisting it—feel its flow, 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, as the wind itself… and destroy everything!"
The wind here was even more violent, like an invisible giant hand tearing at the body. One careless step could send someone tumbling off the cliff.
"Your foundation is complete. It's time to begin training in [Total Concentration Breathing]…"
"Total Concentration Breathing requires you to further strengthen the breathing method I taught you before. Expand your lungs, send oxygen into every blood vessel in your body, accelerate your blood flow and heartbeat!"
"By doing so, your body temperature will rise rapidly, your bones and muscles will burn, and with a human body, you'll obtain power equal to that of a demon!"
Standing at the base of the mountain, Arasaki spoke solemnly. "Asuka… starting today, you will climb to the summit bare-handed every day. Once there, you'll practice Total Concentration Breathing and your basic sword forms, then climb back down."
"When you can finish all of this within two hours, come find me."
"Train with the resolve to die. Do your best."
Arasaki Tetsushin offered no further instructions, leaving Asuka alone.
He believed that even on his own, the flames in the boy's heart would ignite and drive him to complete his training.
At first, the greatest challenge was climbing the mountain in the raging wind.
The howling gales threatened at every moment to hurl him into the ravine below, smashing him into pulp. Yet after gradually familiarizing himself with the mountain paths, this instead became the easiest part.
At the summit, the fierce wind poured into his nose and mouth. The thin oxygen made breathing itself extremely difficult, let alone maintaining Total Concentration Breathing.
His body swayed violently under the wind's assault. Every swing of the sword was arduous, his movements badly distorted.
But he did not retreat. Instead, he faced the wind head-on, breathing more deeply, adjusting his center of gravity and points of exertion with increasing precision.
He struggled within the gale like a lone wolf fighting a storm—blown off balance again and again, only to steady himself once more and swing the wooden sword infused with unyielding will.
The time required for training continued to shrink, until he could complete everything in roughly one hour.
After several months, Asuka's skin had grown dark and rough from the mountain winds, yet his eyes became ever sharper, like a blade honed by frost and gales.
His footing atop the peak grew steadier, his sword swings increasingly fluid even within the raging wind. He could even faintly borrow the wind's momentum to adjust his angles of attack.
When he next appeared before Arasaki Tetsushin, the man had no intention of personally testing whether Asuka had met the standard. Instead, he brought him to the rear mountains of Hayama, to a secluded training ground.
Ancient trees towered overhead, their dense branches blocking out much of the light. The place felt both quiet and dangerous.
For the next year, aside from Miss Rika, who entered and exited the rear mountains daily, and Arasaki Tetsushin, who occasionally emerged to instruct other disciples, no one ever saw Asuka again.
In Asuka's eyes, Hayama's four seasons were reduced to four different winds of the training grounds:
The gentle breeze of spring carrying the scent of new buds; the scorching, dry winds of summer.
The desolate autumn gales rolling fallen leaves along; and the biting winter winds that cut into flesh.
Asuka's body was long since covered in scars.
There were bruises from sparring with wooden swords, cuts from climbing rocky cliffs and scraping against sharp stones, scratches from branches while moving through dense forests, and countless bandages from forcibly pushing past his limits—injuries to tendons and even bones.
Before old wounds could fully fade, new ones layered over them.
These marks covering his body were proof of his desperate pursuit of strength.
Time passed, seasons came and went.
By now, Nanajūhachi Asuka had spent a full two years at Hayama, the land where the Breath of Wind was passed down.
Under Arasaki Tetsushin's guidance—harsh to the point of cruelty—Asuka's physical abilities were driven to the limits of an ordinary human. His once-slender frame was now wrapped in resilient muscle, lines smooth yet explosive, every inch of his physique containing the power of the wind.
More importantly, he finally began systematically learning the sword forms of the Breath of Wind.
From the First Form to the Ninth Form, Arasaki Tetsushin demonstrated each technique and shared his insights.
Asuka learned quickly. His body instinctively seemed to harmonize with the wild, ever-changing nature of the wind. Though the power was still lacking, he had already grasped the fundamental momentum and principles. What remained was refinement.
His swordplay lacked Arasaki's flawless, masterful composure, but it was filled with raw savagery and brutal vitality—like a sudden hurricane tearing across the wilderness without reason.
In addition, Arasaki noticed that whenever Asuka fully immersed himself in the sword forms of the Breath of Wind, there was always a faint, barely contained power about him, as if it were on the verge of erupting at any moment…
"Is it the natural breathing used when hunting demons…?" Arasaki was not entirely sure.
Moreover, no matter how strong Asuka's body became or how refined his swordsmanship grew, the light in his eyes never changed.
When facing Arasaki Tetsushin, who taught him his skills, or Rika, who had always treated him gently, his gaze would soften slightly, carrying an almost clumsy sense of trust. But at all other times, his eyes were cold and distant.
Like a ferocious beast temporarily taken in—well-fed, claws sharpened, yet never truly letting down its guard against its surroundings.
Arasaki Tetsushin saw all of this clearly.
Having experienced countless battles on the brink of life and death, and having taught disciples of every kind, he knew well that great power without a corresponding state of mind could easily slide into a dangerous abyss.
Often, Arasaki would stand alone in a quiet corner of the rear mountains, watching Asuka practice his sword in solitude, saying nothing.
He knew he was not skilled in gentle guidance or emotional comfort. All he could give Asuka was the strictest training, the most solid techniques, and demands bordering on the unforgiving.
He believed firmly that a strict master forges outstanding disciples, and that only through a thousand hammerings does steel become strong.
And this child reminded him of another student.
Compared to that child, Asuka lacked even the last thread of protection and bonds. He was indeed someone worth worrying about.
"Did I make the wrong choice…?" Arasaki Tetsushin would occasionally ask himself. "Did I focus too much on tempering his body, while neglecting the emptiness in his heart? After gaining even greater power, will he instead lose his way…?"
This thought lodged like a thorn in the old man's heart, lingering for a long time.
Until one day not long after, Hayama's silence was shattered by a set of familiar yet slightly rough footsteps.
The newcomer was tall and powerfully built, wearing the dark green uniform of the Demon Slayer Corps. Draped casually over it was an open white haori, emblazoned with a massive, ferocious black character for "Slay," as if intent on crushing all demons beneath its murderous intent.
He had unruly silver-white short hair, and several deep scars crossed his face—most notably one that slashed diagonally from his forehead to his cheek, adding to his vicious aura.
Most striking of all were his eyes, sharp like a bird of prey's, flashing with near-maniacal battle lust and undisguised edge, as though he might pounce and devour someone at any moment.
An invisible, suffocating pressure radiated from his body.
It was the terrifying presence forged only through countless struggles on the edge of death, bathed in demon blood.
The current Wind Pillar of the Demon Slayer Corps—Shinazugawa Sanemi.