Rokuro, admiring the moonlight from his hiding place, looked at his still-not-fully-regrown arm with immense depression in his heart.
'What was the deal with that kid... Why did one slash from him directly block my flesh regeneration? Even after so many days, I still haven't fully recovered....'
He wasn't the type who enjoyed fighting. He didn't know much about the Demon Slayer Corps, but he had vaguely heard of an origin Breathing Style circulating among them that could cause immense damage to demons.
'But weren't the inheritors of that Breathing Style all killed by Muzan-sama long ago?'
'And no matter how you looked at it, this kid was clearly a Wind Breathing swordsman, just like that woman. How could he....'
Twang—!
A biwa sounded.
Rokuro only felt the ground beneath his feet disappear, and his entire body plunged down!
At the same time, three other demons also heard the biwa.
Lower Rank Three - Wakuraba, was aimlessly wandering through the mountains, enjoying the pleasure of torturing and killing lost travelers, when suddenly drawn by an ethereal biwa sound.
Lower Rank Six - Kamanue, was in the middle of arranging ornaments in his home when, upon hearing the biwa sound, he was suddenly pulled by an unknown force into an unfamiliar space.
And another, Lower Rank One - Enmu.
He was much more relaxed and cheerful. Admiring the tattoos on his face in the mirror, a sickly satisfied smile curled on his lips.
After the biwa sounded, he seemed unsurprised, calmly spreading his arms and plunging through the floor.
Thud! Thud! Thud!
Moments later, aside from Enmu, who maintained his elegance and fervor as he landed smoothly,
the other three demons were all roughly dumped onto a smooth tatami mat, landing in a miserable heap.
They almost immediately scrambled to their feet, panicked and bewildered as they surveyed this strange domain.
The Infinite Castle.
This was a nightmare space that completely defied the laws of physics.
Enormous and ancient wooden structures layered and interlaced. Countless corridors, pavilions, paper doors, and pillars were stacked at unimaginable angles, suspended upside down in the air, forming a vast and chaotic labyrinth.
Gravity had lost its meaning here. The sense of direction, like up, down, left, right, was utterly distorted.
Dim paper lanterns emitted a faint light from corners or overhead. The air was thick with the smell of rotting wood and a faint, lingering scent of blood.
Aside from Enmu, the three Kizuki were all somewhat uneasy, nervously looking around.
"What's going on... All Lower Ranks?" Kamanue thought nervously: "Where did Lower Four and Lower Five go? Why are there only four Lower Moons?"
He looked above him, where a black-haired woman with her eyes hidden behind dark hair sat, holding a biwa that emanated a bloody aura.
"Where is this? Is it that woman's Blood Demon Art?"
Amidst the unease of the three Kizuki as they exchanged glances, the shadows in the space slightly writhed.
An ice-cold, bone-chilling aura surged into their hearts.
A woman's figure walked silently and soundlessly from the shadows.
She wore a magnificent dark kimono, its intricate patterns shimmering with exquisite stitching in the dim light. The wide sleeves swayed gently with her steps, revealing a pale wrist.
Her jet-black hair was swept up meticulously at the back of her head. Her features were practically flawless, like the most delicate porcelain.
If not for those scarlet, inhuman vertical pupils, Kamanue would have almost thought he was looking at some kind of oiran from the pleasure quarters.
"Bow your heads. Kneel."
Hum—!!
An intense wave of fear washed over them. The dread within their blood began to surge.
Almost simultaneously, the several Kizuki involuntarily knelt, prostrating themselves humbly and reverently on the ground.
'It was Muzan-sama's voice! Damn! Because his appearance and aura were a bit different, I didn't recognize him in time to properly worship!'
Kamanue wished he could slap himself twice. How could he be so stupid? Why didn't he realize this 'woman' was Muzan-sama!
The woman before them was the progenitor of all demons, the source of all evil… Kibutsuji Muzan!
This was not his true appearance, but a disguise he used to conceal his identity. He usually appeared in a male form, so it was no wonder Kamanue didn't recognize him at first.
"You are indeed very stupid, and not just in this matter." Muzan's voice was full of chilling cold.
'Eh?' Kamanue shuddered.
'Could Muzan-sama actually read my thoughts?'
Before he could speak, Muzan spoke again, coldly:
"Lower Rank Four and Lower Rank Five are dead. Both died on the same day."
"There is only one thing I want to know: Why are the Lower Moon Kizuki so weak?"
"Did becoming one of the Twelve Kizuki end it? Why haven't you eaten more people? Why haven't you grown stronger? At least become somewhat useful to me."
"For the past hundred years, the Upper Moon Kizuki have never changed. They are the ones who kill batches of Hashira-level swordsmen. And you?"
His voice, his gaze, were like a cold wind that froze the air, sweeping over the prostrate Lower Moon demons, making them tremble uncontrollably.
Muzan, with the disgust of someone scanning garbage, fixed his gaze on Rokuro.
"Rokuro." Muzan's voice was so soft it was eerie: "Why is your aura so weak? Like a dog with its spine broken?"
Without any touch, with merely a thought, he could violently invade Rokuro's consciousness!
"Ughhh—!"
Rokuro suddenly let out a bloodcurdling howl, clutching his head with one hand, enduring the pain as if a red-hot branding iron were being directly thrust into his brain!
His memories were being roughly torn open and rifled through by an absolute force! And he could not resist in the slightest!
[Osaki Hachiman Shrine.... A young Demon Slayer boy.... A ferociously shaped grey-black longsword....]
These images flooded into Muzan's consciousness like a tidal wave, making him frown slightly.
'This kid... looked a bit familiar...' Then, he suddenly realized.
As for his most valued and cherished Lower Rank Kizuki, Muzan had specially given Rui extra demon blood and planted a seed connecting to his consciousness, specifically for convenient communication with him.
The moment Rui died, in his rage, he naturally checked the images within the memory seed.
In those final images, besides the annoying boy with the earrings, Tanjiro, and the swordsman using Water Breathing,
this cold-faced boy was also present....
He further churned through Rokuro's sea of consciousness, completely ignoring his agonized wails, carefully observing everything about this boy.
'That serrated longsword, radiating an ominous aura, could actually devour the power of demons?'
Muzan's flawless face creased in a deep frown.
'What was this thing? A new weapon from the Demon Slayer Corps? Or a new kind of Breathing Style?'
This was a variable he had never seen in his long life. A flicker of ice-cold annoyance passed through the depths of his scarlet vertical pupils.
"Useless."
The cold judgment fell. Rokuro's body was suddenly lifted by Muzan's twisted demon hand, which extended and tightly clenched him.
"Why did you try to run? He's not even a Hashira!"
"I'm terribly sorry! Please... please forgive me, Muzan-sama!! I really..."
Splat!
After a violent crushing, Rokuro's body was directly exploded by Muzan in mid-air!
Demon blood splattered down onto the remaining three Kizuki.
Although demons cannot kill each other, this did not apply to the king of all demons, Muzan.
His twisted demon hand was covered in countless ferocious mouths, which quickly devoured Rokuro's mangled flesh and blood, as if such a demon had never existed in the world.
"I think... the Twelve Kizuki only need the Upper Moons. I really can't find any reason for your existence. What do you think?"
The terrified expressions on Wakuraba and Kamanue's faces instantly froze. Fear and anger simultaneously surged within their hearts. They could hardly believe what they were hearing.
But Lower Rank One - Enmu's face flushed, his body trembling violently:
"Muzan-sama! The reason for my existence... is to become your most convenient tool!"
"To devour all your worries! To sweep away all obstacles in your way! To drag those reckless Demon Slayers into eternal painful nightmares! To let them wail in endless despair! Is there anything more important than that?"
"This is the sole value of my life! This is the entire meaning of my existence!"
"If you feel we are useless, then my meaning is to satisfy your desire to kill, to let you vent your anger..."
"This is truly... so blissful...."
He raised his head, spreading his arms. His cloudy eyeballs almost bulged from their sockets.
The corners of his mouth split into an inhumanly enormous grin. It was impossible to tell if this smile was from the heart or deliberately ingratiating, but the fanatical expression on his face was truly hard to imitate.
"Shut up!! Do you want to kill us all?!"
"Be quiet! You madman!"
Wakuraba and Kamanue were scared out of their wits by this insane declaration and instinctively screamed.
Muzan narrowed his eyes, gave a cold laugh, and raised his twisted demon claw high.
"....A smooth-talking brat."
Bam! Bam!
But the targets of his demon claw were Wakuraba and Kamanue.