Only one year remained before the beginning of the main story.
Even Kokushibo, who had endured centuries without impatience, could no longer remain completely calm.
A demon capable of conquering sunlight…
The very thought alone was enough to shake the foundations of fate itself.
Yet Kokushibo understood something clearly his plan was far from flawless.
After all, Kamado Nezuko had initially feared sunlight just like every other demon.
Her eventual immunity had not been something simple or natural.
From Kokushibo's understanding, Tamayo's medicine, Muzan Kibutsuji's blood, and Nezuko's unique constitution had all fused together over time, producing an unprecedented mutation.
That meant merely turning Nezuko into a demon would not be enough.
Her body first needed to fully assimilate Muzan's blood while surviving the transformation without losing her humanity.
And during that process, the greatest problem remained
Muzan himself.
As long as Muzan discovered Nezuko too early, everything would collapse.
Therefore, Kokushibo only needed to ensure one thing for now:
Keep Muzan away from the Kamado family until the proper moment arrived.
Through Kanae's arrangements, Kokushibo arrived at a secluded estate late at night.
The location was hidden deep within territory owned by the Ubuyashiki family, isolated from ordinary civilians and surrounded by silent forests.
Clearly, the Demon Slayer Corps had no intention of allowing a demon to walk freely near their headquarters.
Even so, Kokushibo could not help but feel slightly impressed.
The Ubuyashiki family truly possessed astonishing wealth and influence.
Although Kokushibo himself controlled enormous assets through his overseas trading company, it still paled in comparison to a family that had accumulated resources quietly for over a thousand years.
Before entering the courtyard, Kokushibo activated the Transparent World and carefully observed his surroundings.
No ambushes.
No hidden swordsmen lying in wait.
Within the residence itself, only a handful of presences remained.
Kanae.
Shinobu Kocho.
Several Hashira.
And at the center
Kagaya Ubuyashiki.
Kokushibo stepped inside calmly.
The atmosphere instantly grew heavy.
Tokito Muichiro merely glanced at him with detached indifference, showing no recognition whatsoever. At his current age, Muichiro still possessed none of the memories or instincts that would later awaken within him.
Rengoku Kyojuro, however, froze completely.
The moment his eyes landed upon Kokushibo, his expression trembled.
"…Father?"
The quiet room erupted with tension.
Shinazugawa Sanemi immediately grabbed Kyojuro by the haori collar.
"What did you just say?" Sanemi snarled. "That demon is your father?"
Before Kyojuro could answer, Kokushibo smiled faintly.
"Yo, Kyojuro. You've grown well."
The casual greeting only worsened the situation.
Sanemi's veins bulged visibly.
First, the former Flower Hashira, Kochou Kanae, had become entangled with a demon.
Now the Flame Hashira himself was calling one "Father."
For someone who hated demons more than almost anyone alive, this scene was unbearable.
Just as Sanemi was about to explode, Kagaya gently raised his hand.
"That is enough."
His calm voice instantly quieted the room.
"We are not gathered here tonight to fight among ourselves."
Sanemi clicked his tongue in frustration but obeyed immediately. No matter how violent his temperament was, his respect for Kagaya remained absolute.
Kyojuro lowered his head slightly, confusion and guilt mixing within his eyes.
Meanwhile, Kokushibo stepped forward without hesitation and sat opposite Kagaya.
"Did you prepare what I requested?"
Kagaya nodded softly.
At his signal, a swordsmith reluctantly emerged from the adjoining room while carrying a long wooden box wrapped carefully in cloth.
The man's entire body radiated hostility toward Kokushibo.
For swordsmiths, Nichirin Blades existed solely to destroy demons.
Forging one for a demon was practically sacrilegious.
Had Kagaya not personally requested it, the Swordsmith Village would never have agreed.
Kokushibo accepted the box and slowly opened it.
Inside rested a newly forged Nichirin katana.
The moment his hand wrapped around the hilt, the blade immediately changed color beneath everyone's eyes.
A deep purple hue spread across the steel.
"Purple…" Shinobu murmured in surprise.
Yet before anyone could fully react, another transformation occurred.
Beginning from the base of the blade, crimson color gradually spread outward like burning embers.
A Crimson Nichirin Blade.
The room fell utterly silent.
Even the Hashira stared in disbelief.
Kokushibo narrowed his six eyes slightly.
Interesting.
He tightened his grip.
Without warning
He swung.
Moon Breathing, First Form: Dark Moon, Evening Palace.
A crescent-shaped slash exploded forward, instantly tearing apart the courtyard beyond the room.
The ground split open.
Wood shattered.
The air itself screamed beneath the pressure of the attack.
Everyone present felt their breathing falter.
Even Kagaya's calm expression stiffened slightly.
The attack had been controlled deliberately.
And yet its destructive power still surpassed ordinary imagination.
If Kokushibo truly stood as an enemy before the Demon Slayer Corps…
Could they actually stop him?
As Kokushibo released his grip slightly, the crimson color faded, returning the blade to its original purple shade.
Suddenly
"HAAAH?!"
Haganezuka Hotaru lunged forward like a madman.
Still wearing his grotesque hyottoko mask, he grabbed Kokushibo's arm so aggressively that the mask nearly slammed into his face.
"It turned red!" Haganezuka shouted. "I saw it! It became a Crimson Blade!"
Kokushibo stared at him blankly.
It remained difficult to believe that beneath that ridiculous mask existed an actually handsome face.
"You people should remove him," Kokushibo said calmly.
"He is becoming troublesome."
"Haganezuka-san, please calm down," Kagaya said gently.
After receiving Kagaya's instruction, Kyojuro and several others finally managed to drag the wildly resisting swordsmith backward.
Even while being restrained, Haganezuka continued shouting.
"Let me see it again!"
"You formed a Crimson Blade!"
"Do you understand how incredible that is?!"
The reason for his excitement was simple.
A true Crimson Nichirin Blade had not appeared for centuries.
According to legend, the first wielder of such a blade had been the strongest Demon Slayer in history
Tsugikuni Yoriichi.
The creator of Sun Breathing.
Crimson Blades possessed the power to hinder a demon's regeneration and amplify the destructive force of Nichirin weapons dramatically.
If the Demon Slayer Corps learned how to create them consistently, their overall strength would rise tremendously.
Even Kagaya's interest deepened.
Still, he did not pry.
Every warrior possessed secrets.
And Kokushibo clearly had many.
Meanwhile, Kokushibo himself had fallen into thought.
Why had the blade only partially transformed?
And why had the effect disappeared so quickly?
Was physical grip strength alone insufficient?
He temporarily pushed the matter aside.
There would be time to investigate later.
Kagaya then spoke once more.
"Are you satisfied with the sword, Kokushibo-san?"
Kokushibo sheathed the blade smoothly and placed it beside him.
"It is excellent."
Kagaya nodded.
"In that case… there is another matter I would like clarified."
His gentle gaze shifted toward Kyojuro.
"Your relationship with Rengoku Kyojuro."
Although Kagaya trusted Kyojuro's character completely, the truth still needed to be confirmed openly.
Kokushibo saw no reason to conceal it any longer.
"I met Rengoku Shinjuro first," he explained calmly.
"We got along well enough. At the time, his wife was gravely ill, and I happened to know a physician capable of saving her."
Kagaya listened quietly.
"So Shinjuro left the Demon Slayer Corps because of you?"
"Yes," Kokushibo replied casually. "I threatened him using his family."
Kyojuro's expression changed immediately.
Memories resurfaced from that day long ago the terrifying pressure during the confrontation between his father and Kokushibo.
If events had unfolded differently…
He did not dare continue the thought.
Kagaya, however, seemed to understand more than he revealed.
"I see."
The atmosphere relaxed slightly afterward.
Eventually, the meeting came to an end.
As everyone prepared to leave, Haganezuka suddenly broke free once more and rushed forward desperately.
"Show me the Crimson Blade again!"
Kokushibo ignored him completely.
In the end, several Kakushi members were forced to physically restrain and drag the screaming swordsmith away.
Just before Kanae departed alongside Kokushibo, Sanemi instinctively stepped forward to stop her.
His expression remained dark and conflicted.
Kanae merely smiled softly.
Kokushibo spoke before Sanemi could say anything further.
"Stay with the Demon Slayer Corps."
He had no intention of allowing the Corps to trace his personal movements.
Leaving Kanae among them was far more convenient.
After confirming nobody followed him, Kokushibo returned quietly to his estate before dawn.
Meanwhile, the Hashira dispersed to their respective residences.
Late that night, Kagaya Ubuyashiki sat alone within his room.
His expression remained peaceful as always.
Yet beneath that calm exterior lingered deep concern.
A Crimson Blade had appeared once more after centuries.
But the one capable of wielding such power…
Was a demon.