Kokushibo brought Kyogai back to his estate.
As for Kyogai's eerie manor, the entire structure was simply absorbed into the Infinity Castle by Nakime's Blood Demon Art.
Thus, the "haunted house" rumored among nearby villages vanished overnight without a trace, becoming yet another hidden room within the endless labyrinth of the Infinity Castle.
The moment Kyogai laid eyes on Nakime, his heartbeat nearly stopped.
She sat gracefully before her biwa, expression calm and detached, her pale face illuminated by the dim lantern light of the castle.
To Kyogai, she looked like a spirit from a dream.
Meanwhile, Kokushibo silently observed him using the Transparent World.
He carefully examined Kyogai's physical condition, blood flow, muscular structure, and nervous system.
Honestly, if not for his pitiful talent ceiling, Kyogai's emotional fluctuations alone might have been enough to awaken a Demon Slayer Mark back when he was human.
Unfortunately, talent was absolute.
No amount of obsession could overcome that barrier.
After arriving at Kokushibo's mansion, Kyogai still appeared completely distracted.
His thoughts remained filled with Nakime's image.
"She's… truly beautiful…" he muttered unconsciously.
The next instant
Bang!
Kokushibo kicked him directly to the floor.
"What a pathetic expression," Kokushibo said coldly.
Kyogai hurriedly crawled upright, looking embarrassed.
"B-But she really is beautiful…"
Kokushibo's six eyes narrowed slightly.
"She only has one visible eye. Most humans would find that unsettling."
In truth, Kokushibo was trying to discourage him.
After all, Nakime was essentially Muzan's personal attendant within the Infinity Castle.
Pursuing her was practically asking for death.
"You are quite bold," Kokushibo continued. "To even think about the Demon King's secretary."
"I-I would never dare!"
Unexpectedly, Kyogai became even more emotional.
He pointed excitedly toward his own damaged face.
"I only have one functioning eye too!"
After Muzan destroyed the eye bearing his former Lower Moon rank, his vision had become permanently impaired.
Technically speaking, he and Nakime were both one-eyed.
Then Kyogai added without thinking:
"Besides… even if Lady Nakime looks a little frightening, Lord Kokushibo is much scarier with six eyes!"
Silence.
At that moment, Kokushibo felt as though the entire world harbored malice toward him.
First Inosuke.
Then Kotoha.
Even Muichiro his own descendant always subconsciously asked him to close his eyes whenever the child curled up in his arms.
Only Muzan never openly commented on them.
Although Kokushibo strongly suspected that Muzan simply preferred not to say it aloud.
Muzan's inner thoughts, however, would probably have been:
"When you close your eyes, you resemble your younger brother far more… which is somehow even more unsettling."
Kokushibo exhaled slowly and dragged Kyogai toward a nearby window.
A thin ray of sunlight leaked through a narrow crack in the shutters.
Kokushibo pointed toward it.
"What is that?"
"…Sunlight?"
"Correct."
Then Kokushibo calmly grabbed Kyogai's wrist.
"Now place your hand beneath it."
Kyogai instinctively extended his left hand.
The instant his fingers touched the beam of sunlight
Sizzle!!
Smoke erupted violently.
The flesh began burning away at terrifying speed.
"AAAAAAAHHHHHH!!"
Kyogai screamed miserably and tried to retreat, but Kokushibo held him firmly in place for several seconds longer before finally releasing him.
Then
Slash.
With a single motion, Kokushibo severed the charred section of finger before the damage could spread further.
The detached fragment fell to the floor and instantly crumbled into ash beneath the sunlight.
Kyogai collapsed while clutching his injured hand.
Kokushibo looked down at him with a calm smile.
"Will you continue insulting my appearance?"
Kyogai shook his head so hard his neck nearly snapped.
"N-No! Never again!"
Only now did he fully realize how terrifying Upper Rank One truly was.
Fortunately, Kokushibo had merely punished him lightly.
Otherwise, he would already be dead.
Kokushibo ignored his panicked rambling and instead began considering Kyogai's Blood Demon Art seriously.
Manipulating rooms.
Rotating spaces.
Controlling the structure of an entire building.
If combined properly with Nakime's manipulation of the Infinity Castle…
Then enemies could be endlessly trapped, separated, and crushed within shifting rooms before they even understood what was happening.
The tactical potential was immense.
Thus, Kokushibo suddenly thought of a melody he vaguely remembered.
"Kyogai," he ordered, "play this rhythm."
Then, somewhat awkwardly, he began humming the tune.
At first, Kyogai looked doubtful.
Kokushibo's sense of rhythm was… questionable.
Several beats were off entirely.
Yet once Kyogai corrected the timing and began drumming properly
DON! DON DON!
DON DON!
DON! DON DON DON DON!
The rhythm exploded throughout the mansion.
The melody was strangely infectious.
It carried an irresistible urge to move.
To dance.
To sway along with the beat.
Kyogai's eyes widened.
This was art!
Clearly, the problem had not been the composition itself
It had been Kokushibo's singing.
Meanwhile, deep within the Infinity Castle, Muzan also heard the drumming through Kyogai's senses.
For some reason, the rhythm stirred something hidden deep within him.
His legs twitched involuntarily.
Why…
Why did he suddenly feel the urge to dance?
Muzan immediately pressed down on his trembling knees.
No.
Absolutely not.
He had already restrained certain impulses for nearly half a year.
He would not break now.
And yet
The rhythm was absurdly catchy.
Nearby, Nakime silently observed Muzan's increasingly strange expression.
For a brief moment, she genuinely wondered whether she should summon a toilet into the room.
Or perhaps simply teleport Muzan outside altogether.
After all, even she did not want the Infinity Castle becoming dirty during daylight hours.
Eventually, Muzan lost the internal battle.
"Nakime," he ordered abruptly, "bring me to the dressing chamber."
This time, he surprisingly accepted Nakime's recommendations and selected a far brighter kimono than usual.
Moments later
His body transformed into that of a woman.
Long black hair was carefully arranged.
Makeup was applied flawlessly.
Blush lightly colored his pale cheeks.
When the transformation was complete, Muzan admired himself with satisfaction.
Perfect.
Now then
Just as he prepared to move along with the rhythm
The drumming stopped.
Muzan froze.
"…That's it?"
His eye twitched violently.
"I just finished getting ready."
Naturally, Muzan refused to accept this outcome.
"Nakime," he ordered immediately, "bring Kyogai here."
Nakime plucked the strings of her biwa.
The space within the Infinity Castle distorted instantly.
However, because Kokushibo stood directly beside Kyogai at that moment
Both of them were transported together.
The instant Kokushibo arrived and saw Muzan's appearance, all six of his eyes brightened simultaneously.
Muzan inwardly panicked.
Damn it.
Kokushibo slowly looked him up and down.
The elegant kimono.
The feminine appearance.
The contrast with Muzan's usual cold male voice.
For some incomprehensible reason
Kokushibo found the entire situation deeply amusing.
Muzan immediately turned as though intending to leave.
Unfortunately, Nakime chose that exact moment to pluck her biwa again, shifting the surrounding rooms and accidentally blocking every escape route.
Kokushibo silently praised her timing internally.
He stepped directly into Muzan's path with a faint smile.
"And where," he asked calmly, "does Lord Muzan intend to go?"
Muzan forced himself to remain composed.
Surely Kokushibo would not dare do anything excessive while others were present.
Besides, for centuries Kokushibo had never behaved this strangely toward him before.
Why had he become so unbearable lately?
Muzan cleared his throat.
Still using his male voice, he spoke coldly:
"Kyogai. Continue playing the previous piece."
He assumed this would distract Kokushibo.
After all, Kokushibo had initially reacted rather awkwardly to the combination of a female appearance and a male voice.
Unfortunately
Kokushibo had adapted far too quickly.
In fact, he now found the contradiction oddly entertaining.
The more serious Muzan acted, the funnier it became.
Thankfully for Muzan, Kokushibo had no intention of truly pushing matters too far.
To him, teasing Muzan was merely amusing.
Actually attempting to dominate the Demon King?
That was another matter entirely.
Far away from the Infinity Castle, within the Rengoku residence
Kyojuro Rengoku practiced swordsmanship beneath the evening sky.
Flames seemed to dance around his blade with every swing.
His movements radiated unwavering passion and vitality.
"Kyojuro."
His mother, Ruka Rengoku, called out softly from the veranda.
Kyojuro immediately stopped training.
"Mother!"
Ruka hesitated briefly before asking:
"Do you still maintain contact with… that man?"
Though Kokushibo had once saved their family, Ruka still could not entirely accept the existence of a demon connected so closely to her son.
Kyojuro understood immediately whom she meant.
"Father?"
He shook his head.
"It has been quite some time since we last met."
Then his expression grew serious.
"Even so… I believe Father is not an evil demon."
Ruka remained silent.
Kyojuro placed a hand over his chest.
"Mother, please do not worry."
"If Father were ever to harm innocent people before my eyes…"
His fiery gaze sharpened with determination.
"I would stop him."
Though one sentence remained unspoken within his heart.
Not kill him.
Never kill him.
Even if he could never defeat Kokushibo, Kyojuro would still stand before him without fear.
And if one day Kokushibo truly required human flesh to survive
Then Kyojuro had already decided long ago.
He would offer himself first.
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