Far away, at the Demon Slayer Corps headquarters—in the main Ubuyashiki residence—Ubuyashiki Kagaya woke drenched in cold sweat.
He lay still for a moment, catching his breath, and realized something had changed. The pressure that had hung over him since birth—the weight he had never known a single day without—was simply gone. The necrotic skin that had ached along his face for years felt, without warning, clean.
It was like the moment after DIO turned to ash: every member of the Joestar family who had been affected recovered almost overnight. By the same logic, the incurable illness that had clung to Ubuyashiki Kagaya since birth—twenty years of it—dissolved naturally of its own accord.
Kagaya was twenty years old, but his body had long since aged to resemble a dying elder's. And yet from some moment tonight forward, he felt life returning—a warmth he hadn't known since childhood, before the disease took hold, when he could still swing a Nichirin Sword without his arms shaking.
This was not a dream.
He looked at his sleeping wife and children and did not wake them. He steadied himself, breathed, and slipped out quietly. Outside, he summoned his crows and sent them out with a single message for every Hashira scattered across the country:
Kibutsuji Muzan is dead.
Impossible—and yet the truth of it was written plainly in his own body. The question was who. Certainly not the Demon Slayer Corps—he would have known. A chance encounter with one of his own members? But who among them had the power to do it?
And if not the Demon Slayer Corps, then a demon? Muzan held absolute power of life and death over his demons—his dominion was total, inviolable. No demon could raise a hand against him.
Not a demon, and not a human by any ordinary measure. The reasoning narrowed to one answer.
...
...
All who were connected to Kibutsuji Muzan felt his death in that same instant—his descendants in the Ubuyashiki bloodline, and the demons who carried his blood through their veins.
Ordinary demons were thrown into disarray, but not crisis. It was the Twelve Kizuki who nearly came apart at the seams. From those stationed below ground in Infinity Castle, to those ranging freely across the country, to those of Muzan's inner circle busy tracking down the Blue Spider Lily—every one of them abandoned whatever they were doing and turned back at once.
This was an upheaval without precedent in centuries of demonic history. The progenitor. The absolute sovereign. Dead.
None of them had ever allowed themselves to imagine it.
Because the only enemy of demons was the Demon Slayer Corps, and Muzan's followers had always kept the Corps' movements under watch. Muzan himself was hidden so thoroughly that he had rarely shown his face. How had this happened?
But reality didn't stop for disbelief.
Infinity Castle existed somewhere underground—a space that operated like a warped puzzle box, built in the Japanese style: a disorienting labyrinth of tatami rooms linked by staircases that ran in every conceivable direction, the geometry folded and inverted on itself until a single glance made the eyes slide sideways and the stomach turn.
This was the stronghold of the demons, with Muzan at its center. Its existence was known only to a handful of Upper Rank demons.
The castle was usually quiet. Muzan traveled frequently; the Twelve Kizuki kept to their own domains; it was only when Muzan summoned them that they gathered. Tonight it was considerably less quiet.
A man with long hair and a purple haori stepped in.
No one dared look at him sidelong, even though he was dressed like a Demon Slayer. Not even Doma or Akaza would have hesitated before calling him "Kokushibo-dono."
Kokushibo—Upper Rank One. The strongest of the Twelve Kizuki. Every other rank had turned over more than once across the centuries, but Upper Rank One had never changed—not before tonight's news, and not after.
"Oh. What a strange-looking little thing you are."
Inori could not stop herself.
The man's face had six eyes. The normal pair held the characters for Upper Rank, One—and four more ran across his forehead and cheeks in a row, like the compound eyes of a spider. Deep red markings crossed his forehead and ran from his chin down to his throat. He carried a Nichirin Sword that had transformed into something strange.
That was the first thing out of her mouth upon seeing him.
Kokushibo's brow drew down slightly. He studied this girl he had never seen before with measured curiosity.
She appeared to be sixteen or seventeen. The face was striking—even he, four hundred years old, found himself pausing at it. She was seated at a low wooden table, a piece of botamochi in her hand and the remnants of it at the corner of her mouth, one leg thrown over the other in the most casual possible posture.
This was wrong. Muzan was dead; the Twelve Kizuki had been called here for an emergency assembly; the two Upper Ranks who'd endured for a century were both standing—and this newcomer was sitting there eating sweets.
Nakime sat in her corner with her biwa, silent as ever. Two Upper Ranks standing. One girl, seat taken, snacking without a care.
Something about this picture was off.
"Who are you? Someone new?"
He was curious, not offended.
"You're Upper Rank One—Kokushibo-dono—aren't you." She said it without making it a question. "From today, you'll be answering to me. I'm the new master who will rule over you in his place. My name is Inori."
She delivered this with a smile, then took another bite of botamochi. No ceremony whatsoever.
"What is the meaning of this?" His six eyes turned as one to the other two. "Both of you."
Kokushibo was surprised—but not panicked, not angry. Whatever he felt, he held it still.
"She killed Muzan-sama, Kokushibo-dono." Akaza's answer was flat.
"That is not possible."
Kokushibo said it without hesitation.
"Muzan can suppress any demon's abilities outright. There is no demon who can defy him."
"She isn't a demon," Doma said, picking up the thread. "Not the way Muzan's blood creates. She didn't come into this through infection—she is a truly perfect demon. And she can walk in sunlight."
"..."
All six eyes contracted to points simultaneously.
He knew Muzan's history. He knew how it had all begun—the medicine of the Heian period, the unintended transformation. And if someone had, after a thousand years, re-created that same result through that same means—then Muzan losing to her was not difficult to understand at all.
Kokushibo was not content with this. Of course he wasn't.
But he was also clear-eyed enough to know that he could never have defeated Kibutsuji Muzan himself. The terror of the man had taken root too early, too completely—reinforced with every year of submission, in four centuries' worth of accumulated dread. Whatever his personal feelings had been—and they were complicated—the power gap had always been absolute.
But this girl had done it.
Kokushibo didn't find it surprising, when he thought about it. She was a higher-order existence than Muzan. Where Muzan had spent a thousand years chasing sunlight—climbing toward a mountain peak he could never quite reach—this girl had been born already standing on that peak, in full daylight.
Muzan must have died deeply frustrated.
The way Kokushibo himself had once been frustrated—knowing, without room for argument, that his gifts would never equal his brother's. It couldn't be helped. Some people were simply born at different altitudes. Muzan. You once mocked me for my incompetence. I wonder if you ever imagined a day like this could come for you too.
—You may have been exceptional among ordinary men. But the moment a true equal appeared—you crumbled that easily?
Knowing the unbendable Muzan had been brought down by this small, languid girl—Kokushibo felt, unexpectedly, something very close to satisfaction.
He had never liked Kibutsuji Muzan. He had not become a demon for Muzan's sake. He had become one for a single reason: to surpass his brother. Fame meant nothing. Authority meant nothing. He had no interest in ruling lesser demons. He wanted only to be stronger—endlessly, pointlessly stronger.
And Muzan had already proven weaker than Inori. Which meant her blood was stronger than Muzan's. Which meant, perhaps—
If she were willing to share it, he might finally overcome the sun.
Anything was negotiable, as long as the price was strength.
Kokushibo—Nichirin Sword in hand, the blade transformed and strange—dropped to one knee and bowed.
"My respects, Inori-sama."
"Kokushibo-dono, I find you fascinating." Inori finished her botamochi, placed her hands on the table, and leaned forward. The dark red of her eyes caught light. "A demon who uses a sword."
"Would you be willing to tell me your story?"