It was a very peculiar space.
What made it peculiar was the chaotic arrangement of the buildings, presenting a very eerie layout.
Some were upside down, some were separated from each other, some overlapped like blocks, and some even sat directly on the walls and ceilings, giving one a feeling of entering a dream or a kaleidoscope, very discordant.
No one knew where this was—or rather, those who knew of this place were generally not human.
*Plink-Plonk!*
At a certain moment, as the sound of a biwa being plucked suddenly resounded, a figure suddenly appeared as if by teleportation.
"Where is this...?"
Looking left and right, the figure was momentarily startled, then immediately recognized this place.
"Infinity Castle?"
Infinity Castle, a castle unknown to most but indeed existing in this world.
It was the supreme headquarters of the Twelve Kizuki that was not located in any particular spot on the ground but was like this, in a strange space.
Now, someone had clearly summoned demons here, calling forth the few remaining Upper Ranks of the Twelve Kizuki.
For example, the figure who had just appeared.
Peach-colored short hair, body covered in deep blue tattoos.
Clearly, it was none other than Akaza who had once been considered dead by Riezel before.
Meanwhile, just as Akaza appeared, another figure approached him from behind.
"My, my, isn't this Lord Akaza?"
Saying this, the newcomer approached Akaza affectionately, smiling brightly.
He was a young man with platinum blond hair and irises that shimmered in a rainbow hue. He wore a red turtleneck with a design that made it look as if the area between his neck and upper chest was covered by a black substance, which seemed to be dripping slightly down his body and repeating at his wrists and hands, as well as on the small circular bloodstain on the top of his head.
He had a slender build, taller than Akaza, and the Japanese characters for 'Upper Rank' and 'Two' were inscribed in his rainbow-like eyes, revealing his identity to those who saw them.
Yes.
He was none other than the Upper Two, ranked second among the Twelve Kizuki, a demon just below the Upper One—Douma.
"Long time no see, how have you been lately?"
Douma reached out his hand, seemingly intending to rest it on Akaza's shoulder. However, before it could happen, Akaza suddenly punched his outstretched hand, the force was so strong that it instantly exploded his hand.
"Don't touch me."
Akaza looked coldly at Douma as if saying, 'I'll kill you if you dare to reach out your hand again.'
Such a vicious attitude, not even shown when facing Riezel, was now displayed by Akaza. It was evident how much disdain this Upper Three held for the Upper Two.
Surprisingly, Douma seemed unperturbed.
"You're really heartless, y'know? Clearly, I was just showing concern for you."
Douma shook his severed hand, which regenerated in a second, like a torn cloth coming back to life. If Demon Slayers were to witness this, they would surely be astonished by his regenerative ability that could restore severed limbs in the blink of an eye.
"Well, looks like you're doing just fine then." Douma added with a smirk. "I thought after you got your head chopped off once, even if you miraculously survived, there would be some lingering effects."
"Wanna give it a try?" Akaza's attitude remained icy. "If you want, I can twist your head off your neck right now."
"If that would make you happy, I'm happy to oblige!" Douma's smile didn't waver. "Or should I just twist it off myself for you? You can take it home if you like!"
Although Douma seemed to be joking, Akaza knew that if he agreed, this man wouldn't mind twisting his own head off.
"Tch..."
Akaza clicked his tongue in annoyance, emanating an ominous aura from his whole body. Just as he was about to launch an attack on Douma, a deep voice sounded, stopping him.
"That's enough..."
The deep voice rumbled like distant thunder, reaching the ears of Akaza and Douma, causing both to turn their heads to the side.
Over there, appearing seemingly out of nowhere, stood another figure.
It was a man wearing a kimono with a purple-and-black hexagonal pattern and black hakama pants, his long black hair tied up into a high ponytail. He also had red flame-like markings on the top left side of his forehead and the bottom right of his chin, while a sword hung at his waist, resembling an ancient samurai.
However, what was peculiar was that he had three pairs of eyes on his face with yellow irises and red flesh sclera that had black straight lines diverging from each iris, with Japanese characters engraved in the middle pair.
Left Eye - Upper Rank.
Right Eye - One.
From this, it was clear that he was the strongest of the Twelve Kizuki, ranked only below the Demon King, the Upper One.
"Kokushibou..."
Akaza glared at the newcomer with hostility, fighting intent, and seriousness.
"Lord Kokushibou! Long time no see!"
Douma, however, remained as warm and affectionate as ever, seeming quite pleased to see the strongest of the Twelve Kizuki, the only Upper Rank ranked above him.
Kokushibou ignored their words, instead fixing his terrifying six eyes on the two.
"This is Lord Muzan's personal summons... Those who don't understand the situation... If you continue to fool around... I will personally take action..."
With such words, a pressure strong enough to overwhelm everything around immediately emanated from Kokushibou's body.
Feeling this pressure, Akaza's complexion grew more and more serious, and even Douma stopped acting carefree.
Akaza, Douma, and Kokushibou then looked ahead together, gazing at the one who had summoned them to the Infinity Castle.
It was a woman holding a biwa, dressed in a black kimono, with long black hair, and bangs that hung down to cover half of her face, completely obscuring her eyes.
Apparently, the biwa sound that had been playing in the Infinity Castle from the beginning was her doing.
"Lady Nakime!" Douma greeted the biwa woman sitting at the other end of the building.
"Where is Lord Muzan?" Akaza inquired.
Nakime was in charge of managing the Infinity Castle.
Although she was not part of the Twelve Kizuki and did not have a number, she was Muzan's attendant, specifically assisting him, similar to a secretary. Because of this, the demons of the Twelve Kizuki did not treat her as a mere lower-rank demon.
Moreover, the reason Akaza and the others suddenly appeared in the Infinity Castle was also because of Nakime's Blood Demon Art. In light of this, since she had summoned them with her Blood Demon Art, it was clearly because Muzan had given her such an order.
And indeed, this was the case.
"Lord Muzan has been here for a long time."
As soon as Nakime's faint voice sounded, Akaza and the others felt as though the space in front of them suddenly twisted and distorted.
Soon, a Japanese-style door opened in front of the three, revealing a room that seemed out of place in the Infinity Castle.
It seemed to be a study, filled with various bookshelves and books.
Inside the room stood a tall young man wearing a suit with the coat removed, his skin as pale as paper, bowing his head to read a book in front of a bookshelf with his back to the three. Even when he appeared in front of them, he had no intention of turning around, still engrossed in his book.
However, at the first sight of him, the three quickly kneeled down.
""Lord Muzan.""
Akaza, Douma, and Kokushibou respectfully greeted their king.
Indeed, the young man was none other than the progenitor of demons, the Demon King who had been living in the world for over a thousand years—Kibutsuji Muzan.
He seemed like an ordinary human man, with no trace of anything unusual emanating from his back facing them. Yet, the moment he spoke, the entire Infinity Castle seemed to tremble.
"Gyokko, Gyuutarou, Daki..."
Muzan's voice, devoid of any emotion, sounded indifferent as he spoke.
"They're dead."
With just these words, Akaza, who was kneeling with his head bowed, had his pupils shrink.
"Gyokko and Gyuutarou... dead?!" Douma exclaimed in shock. "What happened?"
Kokushibou remained silent, only lifting his head, his six eyes showing a hint of surprise.
After all, it had been one hundred and thirteen years since there had been any changes among the Upper Rank, and now, all of a sudden, two Upper Ranks had died at once?
What actually happened?
However, despite the shock of the three, Muzan paid them no attention whatsoever, not even bothering to explain how and why.
"I haven't been this furious in years..."
Muzan's voice, carrying a raging fury within its icy coldness, echoed in the ears of the three.
"It's not because of their deaths, but because of your incompetence."
In an instant, a terrifying pressure, as if it could crush anything into minced meat at any moment, permeated the Infinity Castle with unparalleled clarity.
"Because of your incompetence, the Blue Spider Lily has yet to be found, leading to the situation I'm in now."
"What use are you to me?"
"Do you have any value left?"
Each of Muzan's words shook the hearts of the three, shaking their bodies and causing blood to flow from their mouths, noses, ears, and eyes.
Despite this, the three dared not even breathe a sigh.
After all, it was the first time they had seen their king so furious, and they couldn't help but feel a little fearful.
It was well known that Muzan was ruthless and cruel.
Generally, when he was this angry, it usually meant someone had to die to quell his rage. Even if they didn't know what had happened or why their king was so angry, they could only endure it.
Reasoning with him?
Useless.
Muzan was temperamental. He would immediately tear off their limbs if someone tried to reason with him. What made it worse was that even entertaining such thoughts was forbidden since he could even read their minds and hear their innermost feelings.
As a result, even though Akaza, Douma, and Kokushibou were esteemed members of the Upper Ranks and ranked among the top three, they could only bear Muzan's wrath silently.
After a while, Muzan calmed down slightly.
"I'll give you one last chance."
Muzan's voice was cold as he spoke, echoing slowly through the Infinity Castle.
"Get ready... war is coming."