A sharp, overwhelming power erupted from Muzan. The air grew heavy with a biting killing intent that washed over the entire Infinity Castle. For the first time, feeling this boundless energy coursing through him, Muzan Kibutsuji felt truly and completely alive. Even after taking over this world and fusing with his original self, a deep-seated fear had always lingered in his heart.
Acquiring Muzan's immense power had also meant inheriting his countless enemies. The Ubuyashiki family and their Demon Slayer Corps were a constant threat. The mysterious Priest Clan lurked in the shadows, and even the official government of the nation was a force he had to consider. Their survival had always depended on staying hidden, on the forbearance of others.
Muzan hated that feeling—the sensation of his life being in someone else's hands. He refused to experience it ever again. He would no longer be the blade, wielded by fate or fear. From now on, he would be the one holding the blade. And wherever his blade pointed, he would be invincible. This was the absolute control he had always craved.
Now, as he stood reborn, those old threats seemed insignificant. The Ubuyashiki clan was a name and nothing more. The once-mighty Hashira of the Demon Slayer Corps were reduced to just three scattered remnants. And while the God Lord of the Priest Clan had appeared to cause trouble, he was confident that everything was still under his complete control. The key to it all was this new body, this perfect form that had finally broken through every limitation.
Within him, four distinct powers had merged into a flawless whole: the cunning of a human, the unholy power of a priest, the regenerative might of a demon, and the unique biological enhancements from Tamayo's stolen research. His new body contained the best of all worlds—the keen senses of a mortal, the instant healing of a demon, and the spiritual immunities of a priest, all fused into one seamless existence.
He exhaled a long, steady breath, and the crimson light in his eyes intensified. With a single thought, the tentacles of flesh holding Nezuko Kamado vanished, and her body fell heavily to the ground. Before she could even react, Muzan's newly perfected consciousness descended upon her, seizing control of her mind in an instant.
Her body moved without her consent. She rose to her feet, not as a defiant demon, but as a puppet. She walked forward and knelt respectfully before Muzan, her expression completely docile, her will entirely erased.
"So, this is what it means to be a perfect being," Muzan mused aloud.
He could feel the changes clearly. The fundamental weaknesses of demonkind were gone. He no longer needed to consume blood. Decapitation by a Nichirin Sword would not kill him. And most importantly, the sun, his eternal enemy for a thousand years, could no longer harm him. Beyond that, his power as the progenitor of demons had been strengthened on an epic scale.
"Go," Muzan commanded, his voice cold and absolute. "Kill every last member of the Demon Slayer Corps. Find the boy with the flame-like mark on the side of his face. He, above all others, must die."
"As you command," Nezuko replied.
The words were shockingly clear, perfectly articulated. The injuries she had sustained moments before vanished as if they had never been. The old blood of Kibutsuji Muzan that had once defined her was instantly dissolved, replaced by the blood of the new, perfect being she now served. In that moment, Nezuko was also freed from the three great fears of all demons, but at the cost of her soul. She was now bound by an unbreakable loyalty to her new master. This was the ultimate servant Muzan had envisioned, created using Tamayo's research and his own perfected abilities. Only a perfect agent could serve a perfect being.
"This farce," Muzan declared, his voice echoing in the empty space, "is finally over."
His figure blurred, stepping forward into a cascade of light and shadow as time and space seemed to bend around him.
Meanwhile, the battle within the Infinity Castle raged on.
Even a legendary swordsman like Yoriichi Tsugikuni was being pushed back. The combined assault of Kagaya Ubuyashiki, his wife Amane, and the Upper Rank One demon, Kokushibo, was relentless. In his prime, Yoriichi's power was absolute; with one man and one blade, he had been able to overwhelm Kibutsuji Muzan himself.
But this was not the Yoriichi of his prime. He was a lingering echo of that strength, and he could not maintain his peak state for long. To make matters worse, Kokushibo's Moon Breathing and Blood Demon Art constantly suppressed him, forcing him onto the defensive. The flame-like mark on Yoriichi's face seemed to deepen, a sign of his immense strain.
Just as his power began to wane, the God Lord of the Priest Clan finally made her move. From her position above the battle, Chinami unleashed her power. An invisible and terrifying spell spread out like ripples in space, washing over Kokushibo, Kagaya, and Amane.
"Now is the time," Chinami's voice cut through the air, her killing intent reaching its peak.
The spell was of the same origin as the one used against Muzan earlier, but this was its true, undiluted form—an Origin-attribute spell designed for the sole purpose of eradicating demonic power.
Instantly, the three demons felt its effects. A suffocating pressure enveloped them, like an endless black mist draining them of their strength. The demonic energy that fueled their bodies was being choked at its very source.
"What is this?" Kagaya gasped, feeling his newfound power vanish. "Is this the power of the Priest Clan!?"
"To think their God Lord possessed such a technique!" Amane added, struggling against the invisible force.
While Kagaya and Amane were new to their demonic forms, Kokushibo was an ancient being who had slain priests in his past. He knew of their methods, but he had never faced anything like this. The priest he had killed centuries ago was powerful, but his abilities were nothing compared to the God Lord's. Though Kokushibo had some resistance to their spells, he could not completely immunize himself from an attack of this magnitude.
"Yoriichi Tsugikuni, what are you waiting for!?" Chinami shouted from above.
Her words were the signal. The crimson in Yoriichi's eyes blazed with renewed fire. He seized the opportunity his enemies' weakness provided.
Boom!
A pillar of fiery energy shot toward the sky as he raised his blade. The air itself seemed to roar as he prepared his final attack.
"Sun Breathing! Final Form!"
In a single, fluid motion, Yoriichi performed all twelve forms of the Breathing Style he had created. Each slash, each movement flowed perfectly into the next, creating a seamless cycle of unparalleled swordsmanship. When the twelve forms were complete, they merged into one thirteenth form—the ultimate killing blow of the Breath of the Sun.
He had never expected to use this technique on his own brother, or on the descendants of the Ubuyashiki clan he had sworn to protect. The irony was a wound far deeper than any blade could inflict.
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