At the very instant of Nakime's death, the Infinity Castle shook violently, as if struck by a catastrophic explosion.
It felt as though the entire space would collapse at any second, trembling fiercely as it began to crumble, piece by piece.
The ground beneath them shattered abruptly.
Emiya and Kokushibō plunged helplessly downward into a chaotic freefall.
In mere seconds, the entire Infinity Castle would cease to exist.
"[Moon Breathing—Fourteenth Form: Catastrophe, Tenman Crescent Moon]."
At this moment, Kokushibō disregarded the disintegrating environment around him entirely.
His bizarre katana, covered in sinister crimson eyes, suddenly elongated and sprouted countless additional crescent-shaped blades along its sides.
This was Kokushibō unleashing the full extent of his strength.
Numerous giant crescent moon blades exploded outward, accompanied by innumerable smaller crescent projectiles. Together, they surged forth in a torrent capable of flattening everything in their path, spiraling toward Emiya, who had already lost consciousness and was plummeting downward.
He could no longer reverse Nakime's death.
Any demon who hadn't transcended certain limits could never survive decapitation by a Nichirin Blade. Among the Upper Moons, he alone possessed that rare capability.
Of course, Muzan himself had long surpassed those boundaries—only the sun could truly kill him.
Nakime was neither an Upper Moon nor possessed that transcendent resilience. The collapse of the Infinity Castle clearly demonstrated her complete demise.
Now, Kokushibō needed to slay the one responsible for destroying the Infinity Castle—otherwise, he could vividly picture Muzan's furious expression.
Even killing Emiya wouldn't spare him from Muzan's wrath.
Only now did Kokushibō regret not dispatching Emiya immediately, instead giving him repeated opportunities.
Arrogance was a demon's fatal flaw.
Gifted with immortality and regeneration beyond human comprehension, demons inevitably fell victim to a pride just as profound.
Had Kokushibō fought Emiya seriously from the start, as Emiya had done, Nakime would never have fallen.
Humans, by contrast, cherished their fragile, fleeting lives deeply, driving them to risk everything precisely because their existence was finite and precious.
Whoosh—!
Before his deadly moon blades could reach Emiya's falling body, Kokushibō suddenly found himself expelled from the collapsing castle, crashing onto the muddy forest ground outside.
Bright moonlight illuminated his startled expression.
He sensed an all-too-familiar, terrifyingly powerful presence rapidly approaching.
Muzan had already sensed the Infinity Castle's destruction.
"Lord Muzan…!"
A figure slammed into the forest floor nearby with explosive force, uprooting trees and fracturing the earth like a spider's web.
Kokushibō's voice contained a rare tremor, though he managed to retain his composure.
Though Nakime had been invaluable, anyone intelligent knew her importance paled compared to that of an Upper Moon—especially the strongest among them, Upper Moon One.
"What exactly happened here?"
Muzan barely contained his fury, demanding answers from Kokushibō.
While Muzan could share Nakime's vision, he rarely did so unless absolutely necessary. After all, Nakime generally remained quietly in the Infinity Castle awaiting his commands, so shared vision was pointless, revealing nothing but empty hallways.
The Infinity Castle had been Muzan's impenetrable fortress—untouchable even by Tsugikuni Yoriichi. Muzan never dreamed the Demon Slayer Corps could infiltrate and destroy it.
Now it had vanished without warning, plunging Muzan into profound shock and rage.
Nakime had allowed Muzan to instantly communicate with his Upper and Lower Moons. Losing her meant losing this crucial advantage. From now on, Muzan would need messengers—slow, cumbersome, and easily compromised by daytime vulnerability.
Only after losing Nakime did he realize just how arduous his future would be.
"He didn't become a demon?!"
Upon hearing from Kokushibō that Emiya had remained fully human despite receiving his blood, Muzan nearly lost his composure entirely.
First, a rogue demon resembling Tsugikuni Yoriichi had emerged, greatly unsettling Muzan. Now, someone else had rejected his blood outright.
Would injecting Emiya's blood back into his own veins turn Muzan human again?
He shuddered at the horrifying thought.
An act he had barely considered had caused this disastrous chain reaction.
Never had Muzan imagined Emiya could slay both Nakime and Kaigaku, especially with Kokushibō present.
However, Muzan himself hadn't sent Kokushibō to assist Nakime. Kokushibō had been at the Infinity Castle solely because of Kaigaku—a demon he'd personally recommended, one who shared his breathing style. He'd merely visited to guide Kaigaku's training, unaware of Emiya's invasion.
Thus, Nakime and Kokushibō hadn't informed Muzan, confident they could handle Emiya easily.
"His fate is unknown?" Muzan growled dangerously.
"What splendid incompetence!"
Muzan's fist shattered the earth beneath him again. According to Kokushibō, Emiya was surely dead—yet without visual confirmation, no definitive conclusion could be drawn.
In theory, once the Infinity Castle collapsed, all living beings trapped within it should have emerged in the same area, alive or dead.
But Emiya had vanished completely—not a trace remained, neither body nor corpse.
He had simply disappeared.
"Inform every demon immediately: if they encounter a youth with crimson hair, kill him on sight!"
Left without alternatives, Muzan elevated Emiya's threat level to match that of Kamado Tanjirō.
Ironically, Muzan realized bitterly, Tanjirō also possessed striking red hair.
Meanwhile, within the collapsing Infinity Castle, countless rooms, doors, and staircases dissolved rapidly like ink washed away by water.
Yet amidst the disintegrating scenery, a strange wooden door—completely out of place—fell from above, rapidly hurtling toward Emiya's unconscious body.
Pitch-black, resembling space without stars, darkness blending seamlessly into the void surrounding it.
It streaked downward even faster than Kokushibō's pursuing crescent blades.
"—————"
Just as the deadly crescent blades were about to bisect Emiya, the strange door suddenly swung open like a yawning hippo, swallowing Emiya whole.
The fearsome attacks vanished silently, powerless like dust blown away by a breeze.
The door continued its descent, fading quietly into the void.