The Infinity CastleWithin the shifting, endless expanse of the Infinity Castle, silence reigned.
Tatami floors stretched into impossible distances, folding and unfolding as if obeying an unseen will. The faint sound of a biwa echoed intermittently, distorting space itself.
In a quiet chamber, removed from the castle's chaotic geometry, a pot of tea steamed gently.
A tall, long-haired man dressed in a dark, patterned kimono knelt with perfect posture. His movements were precise, measured devoid of unnecessary motion. With steady hands, he poured tea into two cups.
His six eyes hidden beneath lowered lids remained calm.
Once finished, he slid one of the cups forward.
"Please, Lord Muzan."
Seated opposite him was a man of refined beauty pale, composed, and utterly inhuman. His crimson eyes held neither warmth nor restraint, only an overwhelming sense of authority.
Muzan Kibutsuji smiled faintly, though there was no kindness in it.
"You need not trouble yourself with such things."
His gaze lingered.
"You have always been… exceptional. A being who has approached the limits of perfection."
A pause.
"Kokushibo."
The name settled heavily in the air.
Kokushibo lowered his head slightly, his expression unchanged.
"Your praise is unwarranted, Lord Muzan. I merely walk the path I have chosen."
His tone was calm. Respectful. Unshakably composed.
Yet beneath that stillness
Something was different.
Three Days EarlierHe had died.
A frail body, confined to a hospital bed. A life slowly consumed by illness. Regret, frustration, and helplessness had defined his final days.
And then
Darkness.
Followed by awakening.
But not as himself.
When consciousness returned, it came with overwhelming clarity and unbearable weight.
Memories.
Not his own.
Centuries of battle. Endless refinement of the blade. A single, unwavering obsession with strength.
And above all
A name.
Kokushibo.
Upper Rank One.
A demon who stood at the pinnacle beneath Muzan.
At first, disbelief gave way to elation.
He was alive.
The frail, dying body he once inhabited was gone replaced by something incomparably powerful. A body that did not tire, did not age, did not succumb to disease.
But that realization did not last.
Because he knew this world.
He knew how it ended.
This was the world of Demon Slayer.
And Kokushibo… was fated to fall.
The Weight of KnowledgeThe joy of survival quickly turned into something far more complicated.
He was no longer an observer.
He was part of the story.
An enemy of the Demon Slayer Corps.
The very people he once admired their resolve, their defiance in the face of death would one day stand against him.
And he would have to kill them.
The thought lingered heavily.
In his previous life, he had been weak. Powerless. Watching from afar as fictional heroes fought impossible battles.
Now, he possessed overwhelming strength.
A master of Breathing Styles more specifically, the refined and deadly Moon Breathing.
A wielder of the Demon Slayer Mark.
A being capable of perceiving the Transparent World.
Power beyond what most could even comprehend.
And yet
Bound by fate.
After a full day of contemplation, he reached a conclusion.
If he had been given a second life, then he would not waste it in hesitation.
He would live.
Whether as a man… or as a demon.
Return to the PresentKokushibo remained kneeling before Muzan, his demeanor unchanged.
Every word, every gesture carefully measured.
The original Kokushibo had been rigid in hierarchy and discipline. Any deviation could invite suspicion.
Muzan's gaze sharpened slightly.
"You have been… different as of late."
A dangerous observation.
But Kokushibo did not falter.
"I have merely reached a plateau in my pursuit of strength."
A pause.
"Thus, I wish to observe the human world once more. There may yet be something… I have overlooked."
Silence followed.
Then
A faint smile.
"Very well."
Muzan's voice was soft, but absolute.
"Go."
The Human WorldWith the strum of a biwa, space folded.
Nakime silently opened a path, and Kokushibo stepped through.
The air changed.
Cool. Natural. Alive.
For the first time since his rebirth, he stood beneath the open sky.
Even without opening his eyes, the world was clear.
Every movement. Every heartbeat.
The flow of blood within living bodies.
This was the perception granted by the Transparent World.
He exhaled slowly.
His strength was undeniable.
But against Muzan… victory was impossible.
Not through conventional means.
Demons were bound by blood. Control could be exerted instantly.
Rebellion was not an option.
For now.
A Small VillageNight had fallen.
A faintly lit village lay ahead quiet, modest, untouched by the horrors that lurked beyond its borders.
Kokushibo adjusted his form.
His flesh shifted subtly, concealing four of his six eyes. Only a single pair remained visible enough to avoid immediate suspicion.
Then, he closed them.
To others, he would appear blind.
To him, nothing was hidden.
As he approached, a group of villagers stiffened.
A swordsman appearing at night was rarely a good sign.
One man, sturdier than the rest, stepped forward despite his fear.
"E-Excuse me… do you need something?"
Kokushibo raised a hand slightly.
"Do not be alarmed. I mean no harm."
His voice was calm detached, yet not hostile.
"I have lost my sight. Might you tell me… where I am?"
The tension eased, if only slightly.
"This is a village near Mount Kumotori," the man replied cautiously.
Kokushibo stilled.
Mount Kumotori.
A flicker of recognition passed through him.
The place connected to the descendants of the Tsugikuni bloodline.
The family that would one day produce
Muichiro Tokito.
His descendant.
If he could determine the state of that family… then he could place himself within the timeline.
Suppressing the subtle shift in his thoughts, he continued:
"Is there… a family here by the name of Tokito?"
The villagers exchanged glances.
The same man spoke again, curiosity now mixed with caution.
"…Are you related to them?"
A reasonable concern.
Kokushibo inclined his head slightly.
"A distant relation."
Not entirely false.
After all… the blood that ran through them originated from him.
The man relaxed slightly.
"There is a woodcutter Tokito. He lives further up the mountain with his wife."
He hesitated before adding:
"She's with child. If you're kin… you may want to visit soon."
Kokushibo's mind sharpened.
With child.
That detail alone narrowed the timeline significantly.
Everything was beginning to fall into place.
"Understood."
He turned toward the mountain path.
Without another word
He departed.