Kokushibo swore upon his honor that he had only come to investigate the movements of the Monjushiro.
He absolutely had not destroyed that nest of eggs.
Standing deep within the mountains beneath the dim moonlight, Kokushibo stared silently at the shattered remains of a gigantic insect nest scattered across the forest floor.
The broken shells released a disgusting stench into the air.
And directly before him
A Monjushiro unlike any he had ever seen slowly emerged from the darkness.
"…Troublesome."
Kokushibo's six eyes narrowed slightly.
The instant he arrived at the ruined nest, this creature had appeared as if it had been waiting specifically for him.
Someone had clearly destroyed the eggs beforehand.
Yet now the blame had landed squarely on his shoulders.
"Whoever destroyed this nest…" Kokushibo thought coldly, "had better pray I never find them."
Far away, Inosuke suddenly sneezed for no reason.
The massive Monjushiro before Kokushibo resembled a giant praying mantis.
Its body was covered in a dark emerald exoskeleton, while two enormous scythe-like arms gleamed beneath the moonlight with terrifying sharpness.
Then
It spoke.
"Did you destroy… my children?"
Kokushibo paused briefly.
A talking Monjushiro?
That alone was enough to shock him.
However, he immediately answered without hesitation.
"No."
He despised people who shifted blame onto others.
Naturally, he had no intention of taking responsibility for something he did not do.
Unfortunately, the mantis-like creature clearly did not believe him.
Its murderous aura intensified instantly.
Kokushibo sighed inwardly.
"If you already decided I'm guilty," he thought, "then why bother asking?"
Still, rather than attacking immediately, Kokushibo chose to gather information first.
"This is the first time I've encountered a Monjushiro capable of speech," he said calmly while resting one hand on his katana. "Do you possess an individual name?"
The giant mantis tilted its head slightly.
"Monjushiro… is the name of our species."
"My name is…"
It hesitated.
And in that exact moment
Kokushibo moved.
Without the slightest warning, his blade flashed from its sheath.
A merciless crescent slash instantly tore through the darkness.
Utterly dishonorable.
But Kokushibo had lived for centuries.
Honor meant nothing if hesitation led to death.
At the same time, his Transparent World activated instinctively.
Every muscle.
Every organ.
Every weakness.
Nothing could escape his sight.
Yet the instant he observed the creature clearly
Kokushibo's pupils contracted.
"There's no true body…?"
The Monjushiro possessed no central core whatsoever.
Its entire body functioned as a single organism.
But by then, the slash had already been released.
\text{Moon Breathing First Form: Dark Moon, Evening Palace}
Multiple crescent blades erupted outward and carved directly into the mantis's chest.
However
Instead of being cleaved apart, the creature only received a shallow wound.
The Monjushiro glanced down briefly at the cut before finally speaking.
"Call me… Hera."
The next instant
Its scythe arm disappeared.
Kokushibo's instincts screamed.
Too fast.
He barely twisted aside
Slash!
Blood splattered through the air.
Kokushibo landed several meters away before calmly touching the left side of his face.
One of the lower eyes on his cheek had been sliced apart completely.
"…Fast."
If his reaction had been even slightly slower, half his head would have been severed instantly.
For the first time since encountering the Monjushiro species, Kokushibo genuinely felt danger.
This was no ordinary creature.
This was a true monster.
In that moment, all traces of amusement vanished from Kokushibo's mind.
This battle had become a genuine fight for survival.
And the reason for it all
Was still whichever idiot had destroyed those insect eggs.
Far away, Inosuke sneezed again.
Kokushibo slowly tightened his grip around his sword hilt.
Then he activated the Transparent World once more.
This time, he observed Hera carefully.
As long as something lived, it could be killed.
That principle had never failed him before.
Unless…
"It evolves beyond biological limitations entirely," Kokushibo thought grimly.
Still, after several moments of observation, he discovered something important.
Hera truly lacked a central body.
Every inch of her anatomy functioned independently like a colony organism.
Meaning ordinary decapitation might not work at all.
Kokushibo immediately decided to test her defenses further.
His flesh katana suddenly extended outward unnaturally.
Then
\text{Moon Breathing Eighth Form: Moon-Dragon Ringtail}
An enormous sweeping slash covered the entire battlefield.
Countless crescent blades spiraled violently toward Hera.
This time, however, she chose to dodge rather than tank the attack directly.
Kokushibo noticed this immediately.
"So you're not invincible after all."
That alone was enough.
As long as an opponent could be injured, Kokushibo possessed absolute confidence in eventually killing them.
Even gods would fall if their weakness could be found.
The moment the attack ended, Kokushibo instantly retreated backward
But Hera pursued him relentlessly.
Her scythe arm crashed against Kokushibo's blade with terrifying force.
Clang!
The impact shook the surrounding forest.
Kokushibo was forced several meters backward, his hands momentarily numbed from the collision.
"She possesses overwhelming physical strength too…"
His expression darkened slightly.
If ordinary Demon Slayers encountered a creature like this, they would be slaughtered instantly.
At that moment, two faces unconsciously surfaced in Kokushibo's mind.
Muichiro Tokito.
And Rengoku Kyojuro.
Though he rarely admitted it openly, he still cared about them.
After all, bonds formed over years could not simply disappear.
"You are… strong," Hera said slowly.
Her speech remained strange and slightly disconnected, as if intelligence itself was still developing inside her mind.
Then suddenly
Her body began to change.
Kokushibo's eyes widened slightly.
The gigantic mantis form started shrinking rapidly.
Exoskeleton folded inward.
Limbs compressed.
Flesh twisted and reformed.
Until eventually
A humanoid woman stood before him.
Her appearance resembled a human female, though her body was still visibly artificial and insect-like beneath the surface.
Using her own flesh, she formed clothing resembling Kokushibo's kimono around herself.
Strictly speaking, however, the "clothing" was still part of her body.
"…Absurd."
Even Kokushibo felt his thoughts momentarily freeze.
Then Hera calmly tore a long bone directly from her shoulder.
The bone instantly reshaped itself into a blade resembling a katana.
Somewhere in another universe, Kimimaro probably felt spiritually acknowledged.
Kokushibo no longer hesitated.
This creature's evolution rate was terrifying.
If allowed to continue developing, she might truly become uncontrollable.
Thus
He unleashed another technique immediately.
\text{Moon Breathing Seventh Form: Mirror of Misfortune, Moonlit}
The ground exploded apart.
Countless chaotic crescent slashes flooded the battlefield from every direction.
This attack possessed enormous destructive range.
Yet Hera did not retreat.
She simply raised her bone blade and charged forward.
The result seemed obvious.
Her body was shredded apart almost instantly beneath the overwhelming barrage.
Even Kokushibo was briefly surprised.
"…That's it?"
He still had numerous forms left unused.
Surely it could not end so easily.
And naturally
It did not.
The scattered flesh suddenly began moving independently.
Chunks of meat detached themselves completely before rapidly scattering throughout the battlefield.
Kokushibo's expression darkened.
"She abandoned the damaged body itself…"
This regeneration style resembled Muzan Kibutsuji's cellular division.
Without hesitation, Kokushibo stepped forward again.
This time, he decided to erase everything at once.
\text{Moon Breathing Fourteenth Form: Catastrophe, Tenman Crescent Moon}
The forest vanished beneath an overwhelming storm of crescent blades.
Every fragment of Hera's flesh was pulverized instantly into microscopic pieces.
The earth itself split apart under the pressure of the attack.
Once the technique ended, silence returned.
Kokushibo immediately activated the Transparent World one final time and carefully searched the surroundings.
No heartbeat.
No movement.
No life.
Only then did he finally relax slightly.
By now, dawn was approaching rapidly.
Without wasting time, Kokushibo summoned Nakime and returned directly to the Infinity Castle.
However
The moment he disappeared
A tiny tendril slowly emerged from deep beneath the soil.
It stared blankly toward the place where Kokushibo had stood moments earlier.
The sunlight creeping across the horizon did not seem to affect it at all.
Within its simple consciousness, only a single phrase repeated endlessly.
"Moon Breathing…"
"Moon Breathing…"
Inside the Infinity Castle, Kokushibo informed Muzan Kibutsuji about the encounter.
Muzan listened silently.
Then his expression became unusually grim.
"They evolved…?"
Even he seemed unable to believe it.
Such rapid biological adaptation completely violated normal evolutionary theory.
For perhaps the first time in centuries, Muzan felt genuinely disturbed by another lifeform's growth rate.
Kokushibo remained silent.
After all, he himself still could not fully comprehend what the Monjushiro truly were.
Finally, Muzan removed his disguise consisting of a hat and white coat before speaking again.
"Hantengu and Gyokko encountered large numbers of Monjushiro in Shizuoka Prefecture."
His crimson eyes narrowed slightly.
"Will you investigate?"
Originally, Kokushibo had no intention of going.
After battling Hera, he preferred gathering more information first.
Yet for some reason
A strange sense of unease lingered in his chest.
After a brief silence, he nodded.
"…I'll go."