Today, the Infinity Castle was unusually lively.
Powerful Kizuki, wandering demons, and servants of darkness driven by desire gathered together in this twisted place that defied spatial logic and geographical common sense.
Kibutsuji Muzan stood on a floating balcony.
Today he no longer wore his usual refined disguise. Veins bulged beneath his pale skin, and within his crimson slit pupils burned a fury capable of reducing everything to ashes.
Akaza's betrayal, and the deaths of Doma and Daki.
The humiliation of losing control was far more unbearable to him than physical pain.
"Nakime, are they all here?"
Muzan's voice was low, yet it rumbled like distant thunder through every corner of the Infinity Castle.
Nakime, seated within the shadows, lowered her head slightly as her slender fingers plucked the strings of her biwa.
Clang—
With that clear note, several terrifying figures instantly appeared upon the chaotic stairways below the balcony.
"Terrifying... truly terrifying..."
In the shadow of the stairs, a shriveled and grotesque old figure crouched at the edge.
His forehead was covered in wrinkles and swollen lumps, and his eyes were blood-red.
Overwhelmed by fear, his teeth chattered uncontrollably, clacking together without pause.
"Lord Muzan's anger... it's like thunder, ready to shatter these old bones of mine..."
"It was that fool Doma... his incompetence caused Lord Muzan such distress. This certainly isn't my fault..."
"Please don't take your anger out on me..."
As he muttered nervously, his cloudy eyes bearing the Upper Rank mark secretly glanced toward Muzan above.
His pitiful, worm-like demeanor gave no hint that he was the Fourth of the Upper Rank Demon.
"Silence, Hantengu."
Muzan's voice was not loud, yet Hantengu instantly fell quiet like a chicken with its throat grabbed.
"Hehehe, Lord Hantengu is still as timid as a mouse. Such a ridiculous spectacle that one never grows tired of watching."
Another voice echoed from a porcelain jar not far away.
Upper Rank Five, Gyokko, twisted his body—resembling some grotesque fish—and slowly emerged from the narrow mouth of the jar.
Where his eye sockets should have been were instead two constantly wriggling mouths. His tone carried a sickening servility.
"Compared to that coward, Lord Muzan, please look at this mourning vessel I crafted for you!"
"To commemorate the departure of our two colleagues, I collected the finger bones of dozens of craftsmen for decoration. The sheen, the lines..."
"Enough."
"You be quiet as well, Gyokko."
Muzan turned his head slightly, his crimson pupils narrowing.
"I summoned you here not to listen to meaningless nonsense or to admire your cheap art."
"Indeed. You should fulfill your duties as servants and refrain from unnecessary chatter."
A heavy, suffocating killing intent echoed before the two demons.
A swordsman dressed in a purple-black checkered kimono stood there. The pressure he emitted was like a mountain pressing down, causing both Hantengu and Gyokko to reveal wary expressions.
His six eerie eyes slowly shifted. Even before Muzan, his posture retained the rigid dignity of a samurai from the Warring States era.
He bowed slightly, his voice deep and calm like an ancient well.
"You have waited long enough, my lord."
This was Muzan's strongest subordinate.
Upper Rank One—Kokushibo.
Kokushibo spoke with peculiar pauses, a remnant of the strict samurai etiquette preserved from his ancient lineage.
"To replenish the vacant ranks, I have brought a candidate."
According to Muzan's orders, if the Kizuki discovered suitable individuals, they were to bring them back to the Infinity Castle.
The final battle was approaching, and Muzan required more enforcers.
Kokushibo stepped slightly aside.
Under the gaze of his six eyes, a young man wearing a Demon Slayer uniform walked out from the shadows of the pavilion.
The young man's face was pale, and cold sweat streamed down from his temples.
The oppressive aura formed by countless demons within the Infinity Castle had long made it difficult for him to breathe.
When facing Kokushibo alone, he had barely managed to endure. But the moment he stood before Muzan, his already fragile courage collapsed entirely.
His knees buckled, and he fell heavily to the wooden floor.
"M-my lord!"
His voice trembled, but his bloodshot eyes shone with hysterical greed.
"I am the successor of Thunder Breathing! I am a true genius! Give me power and I will become stronger than anyone!"
His name was Kaigaku, a swordsman from Mount Sagiri and the senior disciple of Zenitsu.
Kokushibo looked down at the young man and evaluated him coldly.
"Base character. Ruthless. His obsession born from jealousy will make him strong."
Muzan looked down at Kaigaku from above.
"Thunder Breathing? Do you know a blond, ugly woman? She killed my Daki."
"A blond Thunder Breathing swordsman? A woman... I don't think there was a woman... but there was an ugly man! My junior disciple!"
Afraid of displeasing Muzan, Kaigaku hurried to elaborate, making his answer sound unnecessarily wordy.
"Junior disciple? It doesn't matter. Come here."
Muzan extended his hand.
Sharp claws suddenly grew from the tips of his fingers, and the air filled with the thick stench of blood.
Kaigaku crawled forward on his knees, holding out both hands like a beggar awaiting charity from a god.
"Although you are very weak, I am curious to see how those damned demon hunters will react when they hear about you..."
But Muzan had no intention of letting him drink blood.
Instead, his claw stabbed directly into Kaigaku's forehead.
Demon blood imbued with a curse roared violently into the young man's body.
"AAAAAAHHHHHH!!!"
Kaigaku let out a scream that nearly tore his throat apart as his body twisted unnaturally.
Veins bulged across his skin one after another, and the hazy aura of Thunder Breathing turned a filthy ink-black.
The transformation continued for some time, until Kaigaku collapsed onto the floor, barely alive and unable to scream any longer.
"From today onward, you are Upper Rank Six."
Muzan withdrew his hand and flicked the remaining blood from his fingertips with visible disgust.
"In the final battle, I want you to personally rip out the entrails of the demon hunters."
"Y-yes... my lord..."
Kaigaku knelt on the ground, responding weakly to Muzan's command.
The newly infused blood transformed into arcs of black lightning that crackled between his teeth with each breath.
He felt power unlike anything before.
That overwhelming strength brought twisted satisfaction to his warped heart.
Hantengu, hiding in the corner, muttered to himself.
"Terrifying... the new Sixth Rank? Young people these days are becoming more and more ambitious..."
Muzan ignored Kaigaku and turned his gaze toward the silent woman seated above.
"Nakime, your control over the Infinity Castle has reached its limit."
Muzan clenched his hand in the air, and the entire spatial structure of the Infinity Castle trembled.
"I need you to become stronger. Your eyes must cover every shadow within this space, and your will must spread through every corner of this city."
"I want those demon hunters to hear the sound of your biwa even after death."
"As you command, my lord."
Muzan's tendrils pierced into Nakime's neck, demon blood flowing continuously through them.
Her hair began to grow wildly, spreading like vines across the walls.
At last, a single eye opened upon her face.
Within that eye, the mark spun rapidly before settling into place—
Upper Rank Four.
With a heavy pluck of her fingers, the space of the Infinity Castle expanded at an unprecedented speed.
The original buildings transformed into an even deeper labyrinth.
Countless traps and folded spaces formed within the darkness, and the entire castle seemed to gain a strange, living vitality.
"Next, we will adjust the ranks."
Muzan looked toward Hantengu and Gyokko.
"Hantengu, you will fill the position of Upper Rank Two. I do not wish to see you hiding and crying in the shadows anymore. In the final battle, you will fight with your full strength."
"Summon Zohakuten and drag those Hashira into the depths of despair."
"Gyokko, you will fill the position of Upper Rank Three. If your jars are not filled with the heads of Hashira, then burn yourself to ashes."
The two demons accepted the order in terror.
Although Gyokko was somewhat unwilling to rank below Hantengu, under Muzan's terrifying gaze he could only shake his body frantically in submission.
"And finally, this one."
Muzan turned his head and looked toward a cold corner deep within the Infinity Castle.
A male demon dressed in samurai attire sat quietly on a broken wooden stool.
A strange short spear rested at his waist.
Several layers of yellowed bandages covered his eyes completely, with the words "Mind's Eye" written upon them.
In his hand he held a rough cloth, slowly wiping a heavy shield patterned like a turtle shell.
Noticing Muzan's gaze, he quickly bowed.
"Lord Muzan..."