"Alright—then let's begin your training!" Rengoku Kyojuro said cheerfully when he saw Kazuki.
"Yes. I'll do my best," Kazuki replied, nodding with firm resolve.
After that, Kazuki followed the Flame Hashira to the training grounds at Demon Slayer Corps headquarters. Two people were already there.
Both were girls.
One had long black hair with purple-tinted bangs, a butterfly hair ornament perched atop her head. She had violet eyes and wore the Demon Slayer Corps uniform, with a haori patterned like butterfly wings draped over it.
The other also had black hair and purple eyes. She wore the Corps uniform as well, but with a knee-length black pleated skirt and white boots. Over her uniform was a white cape fastened with a deep pink ribbon at the collar.
The two appeared to be practicing sword techniques. When they noticed Rengoku and Kazuki approaching, Kocho Shinobu and Tsuyuri Kanao paused.
"So you're back, Rengoku-san. How did the mission go?" Shinobu asked with a smile as she sheathed her blade and stepped forward.
Rengoku didn't answer right away. Instead, he glanced back at Kazuki.
Seeing his reaction, Shinobu seemed to understand something. Her smile faded, replaced by a look of sympathy toward Kazuki. Kanao, as usual, wore a faint smile, her expression somewhat vacant.
"This is my newly accepted tsuguko—his name is Kazuki!" Rengoku broke the heavy atmosphere first, introducing him to them in his usual booming voice.
Then he turned to Kazuki and said, "Kazuki, this is the Insect Hashira of the Demon Slayer Corps. She's a highly respected warrior—someone who developed poisons effective against demons and fights without being hindered by physical disadvantage!"
His tone was as bright as ever.
"Insect Hashira-sama," Kazuki said respectfully, bowing to Shinobu after hearing Rengoku's introduction.
Rengoku had already explained the Corps' ranking system to him. As the Hashira were the strongest pillars of the Demon Slayer Corps, Kazuki felt it was only proper to show them respect.
"Rengoku-san, you're flattering me," Shinobu said with a slightly embarrassed smile. "And you don't need to be so formal, Kazuki. You can just call me Sister Shinobu from now on."
"Yes! Sister Shinobu," Kazuki replied, greeting her once more with the same earnest respect.
Shinobu could only smile helplessly at that.
"She's my tsuguko, Tsuyuri Kanao," Shinobu continued, gesturing to the girl beside her. "You two should be about the same age. How old are you, Kazuki?"
"Fifteen," Kazuki answered.
"You're even a year younger than Kanao," Shinobu remarked softly.
"Kanao will be participating in this upcoming Final Selection, won't she?" Rengoku asked.
"Yes," Shinobu nodded.
"Do your best!" Rengoku called out loudly.
Kanao simply returned his words with a quiet smile.
"Well, we've pretty much finished today's training. We'll be heading back now," Shinobu said, then left with Kanao.
After they departed, Kazuki turned to Rengoku.
"Rengoku-sensei, what was that Final Selection you mentioned earlier?"
"The Final Selection is the last trial to become an official member of the Demon Slayer Corps," Rengoku explained.
"It requires surviving for seven days on Mount Fujikasane, where demons reside. Anyone who passes earns their own Nichirin Blade and becomes a Demon Slayer."
After hearing this, Kazuki felt puzzled.
The trial sounded… too simple.
The green-skinned demon he had fought earlier had been easy for him to deal with. Even after learning that demons could only be killed by sunlight or decapitation with a Nichirin Blade, he still didn't find it particularly difficult.
And since the Final Selection only required surviving for seven days, it seemed possible to pass even without killing demons.
Perhaps the demons there are far stronger, he thought.
"Still, the Final Selection is far too early for you," Rengoku said firmly.
"You must first earn my approval before you can participate. So—start training! First, two hundred push-ups!"
"Yes, Rengoku-sensei!" Kazuki responded immediately, dropping to the ground and beginning his push-ups.
At the same time, he instinctively adjusted his breathing. A faint white mist flowed from his mouth.
Rengoku froze for an instant when he saw this.
Breathing Techniques?
I haven't taught him that yet.
Uncertain, Rengoku stepped closer to observe.
"113! 114! 115! 116! ..."
Kazuki focused entirely on his push-ups. His breathing rhythm was perfectly steady. Even after doing so many repetitions, there wasn't a single drop of sweat on his face—his expression remained relaxed.
From up close, Rengoku finally saw it clearly.
It was indeed a Breathing Technique.
It didn't resemble any known style. More than that—it had already reached the level of Total Concentration Breathing: Constant, maintaining Total Concentration unconsciously at all times.
Rengoku fell silent. This was far beyond what he had expected.
"197! 198! 199! 200!"
After finishing all two hundred push-ups, Kazuki stood up. He still wasn't sweating, looking completely at ease.
"Rengoku-sensei, I'm done. What's the next part of the training?" he asked.
Even now, the state of Total Concentration Breathing: Constant hadn't stopped.
Rengoku stared at Kazuki, his heart shaken. After a moment, he asked, "Kazuki… when did you learn Breathing Techniques?"
Kazuki blinked in surprise.
"I haven't learned any Breathing Techniques. You haven't taught me yet, Sensei…"
Then realization struck him. He tapped his forehead and said, "Oh—you mean the way I adjust my breathing? I figured that out when I was five or six. By controlling my breathing, my strength and stamina increase a lot, and I can do things I normally couldn't. That way, I could help Mother—"
Mid-sentence, memories resurfaced, and a wave of sorrow welled up in his chest.
But he quickly steadied himself.
Mother would want me to live on properly… just like how I felt when I saw her wanting to give up back then…
After a brief silence, Kazuki looked up and asked, "So… that's what a Breathing Technique is?"
"Yes," Rengoku nodded.
"It appears to be one—and it has already reached an extremely high level. Total Concentration Breathing: Constant, maintaining Total Concentration throughout the entire day."
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