Chapter 9: Shinazugawa Sanemi
"Hey—where's old man Tetsushin?"
The moment he set foot in Hayama, Shinazugawa Sanemi grabbed a disciple in a light-green kendo uniform by the collar and barked the question, his voice rough and impatient.
He'd come to visit his former mentor—Arasaki Tetsushin, the man who had trained him.
Since becoming a Hashira, Sanemi's days were filled with blood-slick missions and endless battles. Being able to swing by this place he'd once been forged in, even briefly, was a rare kind of relief.
Unfortunately, ordinary trainees didn't recognize him at all. Faced with his ferocious expression, the poor disciple's legs trembled, words catching in his throat—let alone answering properly.
"He's… he's in the back mountain, Sanemi—"
"Oh. Rika."
A light breeze passed.
Sanemi's grip loosened, and Rika slipped into view, steadying the shaken disciple and guiding him aside.
"Are you alright?" she asked gently. "Did he hurt you?"
"Give me a break," Sanemi snorted, still brusque. "I'm not gonna beat people up in my teacher's dojo."
Then he glanced toward the rear slope. "Back mountain, huh? Don't tell me the old man's picked another tsuguko."
Once the frightened trainee was sent off, Rika turned back with a small smile.
"Not exactly. But he is an interesting kid. Sensei's been teaching him in the back mountain for two years now."
Two years?
Sanemi's savage brows lifted. He bared his teeth in a grin—pure, predatory interest.
"Sounds like a decent seedling. I wanna see what kind of thing he is."
The back mountain was where Arasaki Tetsushin reserved his harshest, most essential training—meant only for those he believed could truly inherit the core of the Breath of Wind.
As a former Wind Hashira, Arasaki had the authority to take tsuguko—core disciples.
Compared to ordinary Demon Slayers or trainees, a tsuguko received far more resources: better weapons, better equipment, harsher and deeper training. Naturally, they were expected to possess exceptional talent.
In other words—
A tsuguko's potential nearly equaled the possibility of becoming a future Hashira.
Sanemi himself had once bled and sweated in that very place. Hearing that someone new had been taken into the back mountain lit the competitive fire in his veins.
He didn't alert anyone else.
Alone, he followed the narrow path into the depths of the back mountain.
The closer he got to the secluded training ground ringed by ancient trees, the more restless the air became.
The wind was growling.
Sword intent was slicing invisibly through space.
Soon, he saw him.
At the center of the clearing, a youth was swinging his blade.
The movements were fast and precise. Each swing tore through the air, whipping fallen leaves into spiraling currents around him.
His bare upper body was taut with muscle. Sweat gleamed under the sunlight, dripping with every motion and darkening the earth beneath his feet.
His breathing was deep and steady—each inhale seeming to draw in the surrounding wind, each exhale carrying heat and a low, vibrating hum as air scraped past air.
Sanemi could tell at a glance:
That body had only been forged through relentless training at the edge of human limits.
"Solid foundation," he muttered, crossing his arms and leaning against the trunk of a thick ancient tree, openly appraising the scene.
He could see the embryonic shape of Breath of Wind within the boy's swordplay. It wasn't yet a true Form—but the ferocity, the all-or-nothing drive behind each strike—
Unexpectedly…
It didn't look bad at all.
It felt familiar.
Like catching sight of one's own kind, reflected in another body.
At the same time, Sanemi sensed something far more keenly than Arasaki Tetsushin ever could.
The aura clinging to the boy wasn't the airflow produced by the Breath of Wind.
It was something far more subtle—yet frighteningly sharp and violent.
If it had to be described, it felt like countless invisible, starving fangs opening and closing in the air, carrying an instinctive urge to tear, to gnaw, to devour everything in reach.
Sanemi had never felt this kind of fluctuation from any practitioner of the Breath of Wind. It didn't belong to any breathing style—yet it seemed the boy had forcibly fused it into his swordplay, creating a uniquely destructive, savage style all his own.
"…Interesting," Sanemi muttered, the curve of his grin widening unconsciously as excitement flashed in his eyes.
He could tell that the boy in the clearing hadn't failed to notice his presence. The sudden tension in that straightened back, the sharpened edge to the swirling wind around his blade—all of it spoke clearly.
The intruder had been identified the moment he arrived.
Asuka had indeed felt it immediately.
Sanemi's presence was far too blatant to miss—especially in the quiet isolation of the back mountain.
Over the past two years of training, fragments of Asuka's shattered, murky memories had gradually returned.
He had come to understand that although he now lived as a flesh-and-blood human in this world, he was ultimately different from everyone else.
Asuka could perceive a form of soul energy known as Reishi—and likewise sense the Reishi within Arasaki-sensei and Rika.
Yet when he tried to explain this to Rika, she couldn't perceive what he described at all. She believed it was simply the "natural breathing" Arasaki had mentioned—something innate to Asuka, impossible for others to experience.
That wasn't unprecedented. After all, even the Demon Slayer Corps' breathing techniques had originally evolved from a form of natural breathing no one else could master.
So Rika found nothing strange about it.
And so, aside from practicing the Breath of Wind, Asuka had spent his spare moments learning to control this strange spiritual force, gradually weaving it into his swordsmanship.
Perceiving spiritual pressure—that was one of the most basic applications of this power.
The white-haired man standing with arms crossed atop the tree radiated an overwhelming spiritual pressure—vast, ferocious, and drenched in the stench of blood.
It was utterly different from Arasaki-sensei's mountain-like steadiness.
But this was the back mountain of the training grounds. Asuka trusted that if the presence truly belonged to a terrifying demon, it wouldn't have appeared here in broad daylight without any disturbance.
Suppressing the surge of unease in his chest, he didn't stop training. Instead, he raised his guard to its highest level.
"So strong… absurdly strong. Stronger than Miss Rika—maybe even stronger than Arasaki-sensei…"
"Hey!"
Sanemi finally spoke, his voice loud and impatient, carrying his habitual, commanding tone.
"Kid! That's enough pointless swinging, yeah? Let me see what you're really made of!"
Before Asuka could reply, Sanemi's figure vanished from the treetop in a sharp blur!
Almost purely by instinct—guided by his perception of spiritual pressure and the reflexes carved into his body—Asuka activated the Breath of Wind and slashed hard toward his flank!
CLANG—!!
A deafening crash echoed through the clearing.
Sanemi had already appeared before him, gripping an unsheathed sword and locking it firmly against Asuka's wooden blade.
Seeing the boy's reaction, Sanemi didn't get angry.
If anything, his interest deepened.
That stubborn, wary, feral gaze—
it was practically a mirror.
He snorted, rolled his neck with a sharp crack, and grinned.
"Oh? Not bad at all…"