This was not the crude brawling of street thugs, nor the clumsy swordplay born from brute strength and reckless ferocity as he swung an Asauchi at random.
This strike was more like a resonance between the human body and nature itself—a moment where the body unleashed its ultimate power, pouring it madly into heaven and earth!
The wooden sword swept upward from below, carving out a storm!
"Sensei is being very serious today..." Rika suddenly remarked.
With Arasaki Tetsushin as the center, a tornado formed from pure, violent airflow, erupting straight from the ground!
Boom—!!
The raging wind pressure poured out along Arasaki's wooden sword, instantly sweeping across more than half the training field!
Muddy snow mixed with dust from the grounds, forming a towering sandstorm tornado several meters wide that shot straight into the sky. Like a howling, earth-yellow giant serpent, it crazily bared its fangs at the heavens!
At the edges of the vortex, piercing cutting sounds rang out. Razor-sharp wind blades darted visibly up and down within it. Asuka had no doubt that even the slightest touch would shred flesh instantly!
Moments later, the roaring tornado gradually subsided. The snow, mud, and dust suspended in the air fell like rain, forming a clear circular zone around Arasaki Tetsushin.
He slowly withdrew his stance, the wooden sword angled toward the ground as his breathing steadied.
Arasaki Tetsushin fixed his deep gaze on the stunned Asuka and spoke in a low, powerful voice. "Did you see that? If you want to kill demons, wild swinging and the little bit of viciousness you learned in back alleys won't be enough!"
"If you're willing, I can teach you the Breath of Wind. It will give you the power to fight demons—but you must also bear the responsibility that comes with it..."
"Asuka, do you have the resolve to become a Demon Slayer?"
The resolve to become a Demon Slayer? Asuka froze for half a second, then quickly discarded the thought.
Killing demons didn't mean much to him.
Asuka didn't know where demons came from, but to him, demons eating people was like dogs fighting over food or wolves devouring sheep—perhaps just one of the cruel rules of this world.
He had already repaid the old man's grudge with his life back then. Other demons had nothing to do with him.
Demon Slayer Corps or God Slayer Corps—it didn't matter to him what those people wanted to do.
But power... This old man possessed strong power—power that could be learned!
If he wanted to live... to live better and safer, he had to master greater strength!
"...Fine. How many of those monsters do I need to kill in exchange for this method of training?"
Arasaki Tetsushin looked at him deeply.
The wildness in this boy's eyes had yet to fade—like a lone wolf just taken back into the pack. That desperate will to survive at all costs was the foundation of becoming a powerful swordsman, but it was also a risk...
In these increasingly turbulent times, the Demon Slayer Corps needed more living strength as well...
After hesitating briefly, he made his decision. "There's no need for an exchange. Since you've decided, starting tomorrow, stay and train with us!"
And so, Nanajūhachi Asuka—a stray dog from the very bottom of Rukongai—remained at the Hayama Training Grounds.
In the early days, Arasaki Tetsushin taught him nothing about sword forms or combat.
Every day began atop the mountain, amid the fiercest morning winds.
Arasaki gathered the disciples and had them sit cross-legged on the icy outdoor training field, eyes closed, minds focused, feeling the cold and savage mountain wind.
"Breath of Wind is the most agile and ferocious style—swift and unpredictable like a raging gale!"
"Feel the air enter through your mouth and nose, flow through every inch of your airway, fill your lungs, then slowly exhale!"
"Don't rush your breathing! Imagine yourself as a bellows—every inhale must stretch to the limit! Every exhale must be completely emptied, like a hurricane sweeping the land!"
Listening to Arasaki's instructions, Asuka wondered what was so difficult about this.
He tried a few rounds as told, only to have Arasaki's wooden sword strike his diaphragm without mercy—precise and brutal—leaving him gasping in pain.
"Too shallow!" Arasaki barked. "Rhythm! Maintain a steady, powerful rhythm!"
Asuka struggled back to his feet, gritted his teeth, and forced himself to meet Arasaki's demands to the extreme.
He quickly tasted suffering.
In the violent mountain winds, the air cut like blades, making his chest feel tight. And under Arasaki's orders, they had to breathe far deeper and faster than normal, forcefully sensing every fraction of airflow.
Countless invisible needles stabbed repeatedly into his airways and alveoli. A tearing sensation spread through his lungs—every breath felt like blades scraping through his throat!
After barely ten minutes, his vision darkened, his ears rang, and he broke into violent coughing.
"Hmph! Can't even handle this much hardship and you want to wield the power of wind?" Kenichi scoffed. He was also seated and breathing, but his progress far surpassed Asuka's, so he wasn't nearly as miserable.
He openly mocked Asuka, while Arasaki silently allowed it, observing as Kenichi deliberately provoked the wild boy he disliked.
But Asuka ignored Kenichi's taunts. He simply wiped the saliva from the corner of his mouth with his sleeve, steadied himself, and tried again.
Compared to living day-to-day like a hunted stray, what was this pain?
Arasaki quietly watched the near-obsessive persistence in Asuka, sensing his clumsy, heavy breathing—raw and beast-like, struggling yet refusing to give up. His expression grew solemn.
This child had a ruthless streak... For his goal, he would squeeze out every last ounce of strength he had...
One day. Two days. Three days...
Asuka became the earliest to arrive and the last to leave the training grounds.
Before the morning frost had melted, he was already seated on the icy stone slabs. Even after everyone else left, he remained lost in his breathing trance.
A tearing pain spread through his lungs. Sweat soaked his clothes, then quickly chilled in the cold wind, clinging to his skin like ice—but he endured it.
Sometimes he trained until exhaustion and collapsed directly onto the frozen stone, only to be dragged back to his room by Rika during her rounds.
Yet the next day, he still appeared on time, his gaze even more resolute.
Kenichi's ridicule slowly turned into silence—then into looks of incomprehension.
He watched Asuka fall again and again, only to rise again and again.
This wasn't training—it was desperation, like burning his own life just to grasp a chance at strength.
That ruthlessness made Kenichi feel pressure... even respect.
When Asuka finally managed to maintain that breathing for over half an hour amid the intense pain without fainting, Arasaki at last handed him his first training wooden sword.
"Starting tomorrow, we begin physical training!"
But this was not liberation—it was an even harsher ordeal.
Inside the training hall, Arasaki demonstrated the most basic grip. "Without a solid foundation, even the most dazzling techniques are castles in the air. Burn this into your heart!"
Thus, Asuka began mind-numbingly repetitive basic swing training.
Chop! Slash! Lift! Thrust!
Again and again, day after day, he repeated the simplest, dullest motions.
Both hands gripping the heavy wooden sword, he followed every angle and every measure of force demanded by Arasaki with absolute seriousness.
Every swing had to align with the rhythm of breathing.
Inhale—gather strength.
Swing—explode.
Exhale—recover.
The movements had to be precise. The breathing had to be synchronized.
Kenichi and the other trainees, after completing their required swings, moved on to more complex footwork or sparring.
Only Asuka—like a tireless machine—remained where he was, swinging his wooden sword again and again.
His arms felt like they were filled with lead, each lift agonizing. The rough hilt tore his palms open, blood seeping into the grip. Sweat flowed into the wounds, bringing piercing pain. His waist and back ached unbearably, as if they might snap at any moment.
"Enough! You've already finished today's quota! Are you trying to ruin yourself?" Kenichi finally shouted at Asuka after one session, unable to hold back.
Asuka didn't pause even slightly. Sweat streamed down his tense jawline, dripping onto the wooden floor at his feet. He said nothing.
He didn't know what muscle soreness was. He only knew that when thugs' clubs came down, his back would hurt even more!
Morning. Noon. Dusk. Evening. Even late into the night.
A thousand times. Ten thousand times. A hundred thousand times...
The blisters on his hands burst and healed, burst and healed, until they became thick layers of calluses.
This continued for seven months.
Until one day, Kenichi looked at him with admiration and said,
"...Asuka, you're incredible! The teacher said that starting tomorrow, you can begin [Field Training]!"