If the information was accurate.
Then the gap between Upper Rank and Lower Rank among the Twelve Kizuki was not merely large.
It was a break in the power scale.
A cliff.
His "cheap mentor" could confidently claim he might defeat some of the Lower Ranks in his prime.
If so, then the Pillars, who were stronger than Kazami Koyoshi, should be able to handle Lower Ranks with relative ease.
But the Upper Ranks
Forget defeating them.
Even surviving an encounter with one was, for most Pillars, an extremely difficult feat.
The hierarchy was clear enough that even someone who disliked reading lore could not ignore it.
Upper Ranks far above everything else.
Pillars below them.
Lower Ranks somewhere around Kazami's level.
And himself at the bottom of that particular chain.
Upper Ranks far above Pillars.
Pillars above Lower Ranks.
Lower Ranks around Kazami.
Kazami above Natsuo.
So the late game bosses were basically decided.
Six Upper Ranks.
A Demon King hidden somewhere.
And perhaps the occasional Lower Rank that functioned like a mid boss.
Yet the more Natsuo thought about it, the more something felt wrong.
If the enemy faction was that vicious.
If Upper Ranks could wipe out Pillars.
Then why was the Demon Slayer Corps still using a brutal elimination tournament to recruit new swordsmen?
Wouldn't it make more sense to raise the acceptance rate, recruit more people, and train as many talented candidates as possible?
If a Pillar could not defeat an Upper Rank alone even when fighting to the death.
Then what about two Pillars together?
What about three?
Four?
The number of Upper Ranks was only six.
If the Corps increased its base numbers, the probability of producing Pillars would naturally rise.
More candidates meant more survivors.
More survivors meant more skilled swordsmen.
More skilled swordsmen meant a higher chance of Pillars emerging.
And if there were more Pillars, then squad tactics would become possible.
Two Pillars for one Upper Rank.
A support team for information gathering and rescue.
A coordinated kill plan instead of heroic duels.
Against demons that devoured humanity itself, why would anyone cling to some romantic rule of one on one combat?
Just swarm them.
Mob them.
Overwhelm them.
So long as the Corps did not treat this like a martial arts tournament, the advantage of numbers should be real.
Unless
Unless the Corps' system was flawed.
Unless there was some hidden constraint in the world.
Unless the organization itself had reasons it did not openly explain.
If Kazami had not repeatedly insisted that the head of the Ubuyashiki family, Ubuyashiki Kagaya, was truly benevolent, Natsuo would have already filed the man under "secret mastermind."
The type who hid behind a gentle smile, coldly moved pieces on a board, and treated recruits like disposable resources.
Because the numbers did not make sense.
A high casualty recruitment pipeline while facing an enemy that erased even top tier fighters
That was not strategy.
That was waste.
Perhaps the topic had become too heavy, because Kazami clearly intended to end it.
"Natsuo," Kazami said, standing and collecting the bowls, "rest properly for the next few days."
"When your uniform and your Nichirin Blade arrive, you'll begin your duties as a demon slayer."
He paused, then added with a faint frown.
"If your custom weapon takes longer, you'll have to use an ordinary Nichirin Blade for now."
"And for the next two days, don't push yourself too hard."
"We'll do some partner practice."
"Prepare your body and breathing for missions."
He turned slightly as if to leave.
But Natsuo raised a hand.
"Wait, Kazami san. One more thing."
Kazami stopped, looking back.
Natsuo did not phrase it like a direct complaint.
He wrapped it in the form of a training question.
But the core of it was simple.
His Wind Breathing compatibility was not high.
Only sixty five percent.
That meant for every three achievement points he invested, one point was wasted.
It was not just a small loss.
Over time, it would become a massive bleed.
And that led to an even more important suspicion.
If compatibility affected point conversion, then it likely also affected learning speed.
Skill development.
Sword form execution.
In short, it might affect everything.
If he trained a breathing style with higher compatibility, would his strength jump even if his stats and skill levels stayed the same?
If he found one that suited him perfectly, at one hundred percent, would it become a full body upgrade without changing a single number?
It could easily be a huge improvement.
Fifty percent or more in real performance, simply because the breathing technique fit the shape of his body and the rhythm of his mind.
Kazami did not scold him for being greedy or impatient.
Instead, he sat back down, his expression growing serious and instructive.
He explained patiently.
Breathing styles, whether Wind, Thunder, Flame, Stone, or Water, were fundamentally the same kind of technique.
A method of controlling inhalation and exhalation.
A rhythm.
A pattern.
A way to push the human body's function to its extreme.
It was not a mystical energy.
Not a supernatural aura.
Not the same thing as Blood Demon Arts.
Because it was a technique, it naturally changed depending on the person practicing it.
Different lungs.
Different ribs.
Different muscle distribution.
Different joint structure.
Different stride length.
Different heart capacity.
Different nerve response.
These differences created subtle shifts in how well a style fit someone.
Sometimes the fit was positive.
Sometimes it was negative.
Kazami gave examples.
A person with a large frame, thick bones, and heavy muscle mass would often struggle with styles that demanded sudden explosive acceleration.
Such a person might find a more straightforward power style like Flame Breathing easier to develop, or a stable, grounded style like Stone Breathing.
In contrast, someone with high natural speed but weaker endurance might find certain forms difficult because their body could not support repeated extreme bursts.
Then there were people with talent but weak cardiopulmonary capacity.
They might not survive the strain of styles that pushed the lungs and heart too aggressively.
For them, choosing a style with gentler load could be wiser.
Even temperament mattered.
A person with slow nerve response might find Thunder Breathing's forms sluggish and awkward, not because they lacked courage, but because their body could not fire fast enough.
Someone who was blunt and direct, who always moved in straight lines, might struggle to embody the fluid transformations required by Water Breathing.
These differences were not always dramatic.
Because the five primary breathing styles were all derived from the same ancient foundation.
But enough small differences stacked up could create the feeling that one style was natural while another felt like wearing someone else's shoes.
Still, Kazami emphasized, it usually did not create an absolute divide.
It was not like one style made you a god and another made you useless.
It was more like each style emphasized different aspects of performance.
Some favored burst output.
Some favored sustained pacing.
Some strengthened leg drive and joint coordination.
Some reinforced core stability and grounded power.
And then Kazami pointed out something Natsuo found useful.
Among the five, Water Breathing was the most forgiving.
Its entry barrier was the lowest.
That was why Water Breathing swordsmen were the most common.
If someone could not even adapt to Water Breathing's rhythm and forms, then they would likely struggle with the other four, which were more demanding in specific directions.
Natsuo blinked.
"So the five primary styles don't have the same entry difficulty?"
Kazami nodded.
"This is based on what I've seen, and on the distribution within the Corps."
Stone Breathing was the hardest.
It demanded extreme physical conditioning.
Not just strength, but endurance, stability, and resilience.
Thunder Breathing was also difficult, though in a different way.
It demanded sharp nerve response and strong leg musculature, and it punished hesitation.
Wind and Flame were closer to each other.
Wind emphasized lung capacity, balance, and continuous momentum, and it required the body to maintain control under aggressive movement.
Flame emphasized explosive output in the limbs and direct power, pushing the body into a more straightforward, heavy hitting rhythm.
Water, though forgiving, had its own core demands.
Coordination.
Timing.
Smooth transitions.
The ability to flow from one form to another without breaks.
It was not the strongest by default.
But it was the most widely usable.
Most demon slayers, Kazami said, chose one of the five primary styles.
Only after surviving long enough, after reaching a certain level, did people begin to seriously consider compatibility as a "build problem."
Most recruits were not thinking about optimization.
They were thinking about staying alive.
They trained their bodies.
They sharpened their senses.
They learned how not to die when a demon lunged from the dark.
They focused on endurance and discipline, not on perfect theory.
Natsuo nodded slowly.
It matched his own gamer experience.
Most players rushed to max level before they worried about builds.
Only whales and high level players started early, constructing skill trees and planning synergy from the beginning.
Then he asked a sharper question.
"What if none of the five primary styles fit?"
If the five were designed for the most common "body types," then it was inevitable that some people would fall outside.
A talented swordsman with unusual structure might have low compatibility with all five.
Kazami did not deny it.
The reason the five were called primary styles was because many derivative styles existed.
Over the Corps' centuries of history, there had been swordsmen who used breathing styles outside those five.
Some because they were gifted.
Some because their bodies were unusual.
Some because their minds worked differently.
They would take the core of a primary style and adjust it.
Refine it.
Twist it.
Sometimes they replaced steps.
Sometimes they changed the rhythm.
Sometimes they restructured the forms entirely.
Creating a derivative breathing style.
It was not necessarily stronger.
But it was more suited to the person who created it.
And anyone who could create a derivative breathing style and leave their name in history was not an ordinary swordsman.
At minimum, they were high ranking.
Possibly close to the level of a Pillar.
And Kazami added something that made Natsuo's eyes brighten.
"It's possible," Kazami said, "that the five primary styles themselves were once derived from an even older breathing method with harsher requirements."
In other words, the system was layered.
Ancient root.
Five primary branches.
Countless smaller branches.
Natsuo felt like his mind had opened a new menu.
A hidden skill tree.
A deeper build system.
He began summarizing his new understanding like he was writing notes.
Weapon choice.
Physical conditioning.
Technique.
Sword forms.
Breathing style selection.
Breathing level.
Breathing compatibility.
Each of these was its own multiplier.
Its own separate lane.
Its own independent contribution to final output.
To clear the game, he did not need to perfect everything.
But he absolutely could not afford a glaring weakness.
Not when Upper Ranks existed.
Not when even Pillars died.
Natsuo looked up.
"Kazami san."
"How do I develop my own breathing style?"
Kazami stared at him.
Then his brows rose slightly in disbelief.
"How would I know?"
"I don't use a derivative style."
Natsuo froze.
Huh?
Kazami folded his arms, looking annoyed.
"Creating a breathing style is not something you decide on a whim because your compatibility is low."
"It's the result of years of training, experience, and surviving real combat."
"First master the fundamentals."
"Then you can think about refinement."
Natsuo scratched his cheek.
So it was not an early game option.
It was an endgame feature.
Probably locked behind high level mastery, special conditions, and maybe some hidden trigger.
Still.
Knowing it existed changed his entire plan.
His path forward was clearer.
Learn the five primary styles.
Test compatibility.
Choose the best.
Use the rest as minor investments for attribute returns.
Build a set.
And if he truly reached the level where his body and mind demanded something else
Then make his own.
Natsuo's gaze sharpened with renewed motivation.
"Alright," he said. "Then I'll start by collecting data."
Kazami exhaled as if he had just taken on something troublesome again.
"This brat."
Then, after a short pause, he added.
"But you're not wrong to think."
"Just don't rush."
"And don't play with fire."
(End of Chapter)
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