The enormous spider demon let out a distorted laugh before its body suddenly began to convulse violently.
In the next moment, it began spinning thick layers of silk around itself, forming a dense protective cocoon.
Kokushibo watched silently.
"…A defensive transformation."
Without hesitation, he stepped forward and drew his blade.
A single slash struck the cocoon.
The impact was clean but the result was unexpected.
The blade vibrated in his grip, and a faint numbness spread through his hand.
The spider silk remained intact.
Kokushibo narrowed his eyes slightly.
"Durability above average Lower Moon level…"
Before he could act again, a smaller spider demon dropped from the trees, aiming directly for his blind side.
"Master, be careful!" Rui shouted from behind, still injured but alert.
As a demon, Rui's regeneration kept him functional as long as his head was intact and he avoided lethal Nichirin damage.
Kokushibo did not turn.
A flicker of movement.
Blood Demon Art Thread Prison
The attacking spider was instantly severed mid-air by razor-thin threads before it could land.
Kokushibo glanced briefly at Rui.
"…Efficient reaction," he murmured.
Rui was not weak among the Lower Moons.
His position as Lower Moon Five was not due to lack of ability, but because his power was distributed among the "family" he created through his Blood Demon Art.
Loyalty, however, was absolute.
Perhaps more than even some Upper Moons.
The cocoon suddenly ruptured.
A massive figure emerged.
What stepped out was no longer a simple spider demon.
It was humanoid in shape, over three meters tall, with a grotesque face covered in multiple eyes and a jagged mouth filled with fangs.
Spider-like limbs extended from its back like additional arms.
Even Kokushibo's expression shifted slightly.
"…A complete transformation."
He activated Transparent World, reading its structure instantly.
A refined core… and absorbed humans.
"Did it consume something?" Kokushibo asked calmly.
Rui responded without hesitation.
"It ate Father… and the Demon Slayer Corps scouts."
Kokushibo exhaled faintly.
So it had completed a forced evolution through consumption.
The creature let out a wet, distorted voice.
"Yubi…"
Its name.
Kokushibo stepped forward, gripping his blade.
"…Very well."
He lunged.
The spider demon reacted instantly, meeting him head-on.
Steel collided with flesh reinforced by demonic power.
Kokushibo's eyes narrowed slightly.
"It can block Nichirin strikes bare-handed…"
A rare trait among Lower-class demons.
The creature counterattacked, its claw raking across Kokushibo's torso.
A deep cut opened.
Toxic interference from prior contamination slowed regeneration momentarily.
Kokushibo clicked his tongue and kicked backward, creating distance.
Then
Moon Breathing, Third Form: Loathsome Moon – Chain of Deterioration
Multiple crescent slashes erupted forward.
The spider demon responded immediately.
Blood Demon Art Thousand Thread Barrier
A dense mesh of spider silk formed mid-air, intercepting the slashes and dispersing their force.
Kokushibo's eyes sharpened.
"…Blood Demon Art."
Rui stiffened.
The existence of structured Blood Demon Arts outside Muzan's direct lineage variation was unusual.
Kokushibo recalled Muzan's earlier reports about "mutated demons."
So this was one of them.
The spider demon advanced again, its threads whipping forward like blades.
Rui moved without hesitation.
Blood Demon Art Thread Creation Prison
He intercepted, binding the incoming attack.
But the spider demon's strength overwhelmed him and began dragging him forward.
"Little spider… come here," it hissed, opening its maw.
Kokushibo moved instantly.
Moon Breathing, First Form: Dark Moon – Evening Palace
A clean arc severed the threads and forced separation.
Rui was pulled free.
"…You are useful," Kokushibo stated flatly.
He had no emotional attachment but efficiency was worth preserving.
Elsewhere on the mountain, the remaining spider "family" was collapsing.
The Mother Spider, struggling to maintain control over manipulated Demon Slayer Corps members, was losing stability.
The Sister Spider screamed as her control weakened.
"I can't hold them anymore this place is insane!"
The Mother hesitated, torn between obedience and survival.
But fear won.
"Rui will "
Before she could finish
A flash of flame cut through the forest.
Two heads fell silently.
A blade wrapped in flame reflected the moonlight as the figure passed.
No hesitation. No wasted motion.
Only execution.
At the same time, Demon Slayer Corps reinforcements arrived.
Tanjiro Kamado charged forward immediately upon seeing the devastation.
"These demons…"
Beside him, Sanemi Shinazugawa stepped in with a grim expression.
"Wind Breathing…"
First Form: Dust Whirlwind Cut
Blades of wind shredded multiple spider demons instantly.
Shinobu Kocho and the others moved swiftly to rescue surviving personnel, administering poison treatment and stabilization.
The battlefield began shifting rapidly in the Corps' favor.
"Clear them all," Tanjiro said, voice shaking with anger. "Every last one."
On the mountaintop
Kokushibo paused.
His gaze shifted slightly upward.
"…More humans."
He adjusted his grip.
Rui tensed.
"Something stronger is coming," Kokushibo said calmly.
Then he moved.
Moon Breathing, Sixteenth Form: Lunar Rainbow – Lone Crescent Sky
A wide-range crescent shockwave tore through the battlefield not perfectly precise, but intentionally expansive.
A signal.
A declaration.
Rui understood immediately.
This was no longer a local battle.
It was becoming a full-scale extermination zone.