With everyone's cover fire shielding them, Tanjiro and his companions successfully slipped away from the battlefield and set off to find Nakime.
Inside the Infinite Castle, the stench of demons mixed with the heavy, metallic scent of blood. The odors overlapped and distorted one another, making it impossible for Tanjiro to pinpoint Nakime's scent.
Thus, the task of locating her fell upon Zenitsu and Inosuke.
Tanjiro stayed close to them, guarding their surroundings and ensuring no one interfered as they focused.
Zenitsu calmed his breathing, closed his eyes, and raised his ears sharply, listening with every fiber of his being.
Inosuke knelt down on one knee, raising both hands flat before him.
"Beast Breathing, Seventh Fang: Spatial Awareness!"
Together, the two could sense even the faintest tremor in the air throughout the entire Infinite Castle.
Meanwhile, Yosuke faced the combined assault of Kibutsuji Muzan and the Priest Master.
Using his undying body and overwhelming strength, he barely managed to hold his own, forcing the battle into a stalemate.
Elsewhere, Doma and Hantengu were being driven back by the united assault of the Demon Slayer Corps' Hashira and Hakuji.
And at last—Nakime, who had remained silent all this time, began to move.
As Doma's Lotus Bodhisattva statue was destroyed by the coordinated strike of Sanemi Shinazugawa and Obanai Iguro, Gyomei Himejima seized the moment, swinging his chained flail downward in a crushing strike.
Just before it landed, the sharp pluck of a biwa echoed—
Nakime had played a note, and Doma's position instantly shifted, causing Gyomei's strike to miss.
Zenitsu and Inosuke's eyes shot open simultaneously.
"Found her!"
Tanjiro's face lit up with excitement—he hadn't expected them to locate her so quickly.
"Excellent," he whispered. "But be careful—don't make a sound."
The three crept silently toward the chamber where Nakime was hiding.
Reaching the innermost room of the Infinite Castle, they huddled together, whispering their plan.
"When we go in, Zenitsu—you're the fastest, so you attack first," Tanjiro said. "According to Kokushibo, Nakime controls the castle through her biwa. That's our target—her instrument. The moment you strike, Inosuke and I will back you up."
Zenitsu nodded firmly, agreeing to the plan.
From what Kokushibo had said before the battle, the three believed that while Nakime held the title of an Upper Rank, her individual combat ability was likely even weaker than that of the Lower Moons.
Taking a deep breath, Zenitsu readied himself outside the door and unleashed his technique.
"Thunder Breathing, First Form: Thunderclap and Flash — God Speed!"
With a blinding flash, Zenitsu exploded forward, smashing through the wooden doors in an instant.
Though invisible to the eye, Nakime felt a sudden gust of wind brush across her face—
a surge of killing intent that made her hair stand on end.
She had already sensed the absence of three fighters on the battlefield below and remained vigilant for a sneak attack.
Her fingers twitched, moving to pluck her biwa and shift her position—
but Zenitsu's speed far exceeded her reaction time.
A streak of lightning flashed.
The biwa in Nakime's arms shattered into splinters, and a Nichirin Blade pierced straight through her abdomen.
"Tanjiro! Inosuke!" Zenitsu shouted.
Understanding immediately, the two rushed in.
"Hinokami Kagura: Solar Radiance Thrust!"
Tanjiro leveled his blade, driving a flaming spiral thrust into Nakime's already-impaled body, pinning her firmly to the ground.
"Beast Breathing, Sixth Fang: Palisade Bite!"
Inosuke clamped both serrated Nichirin Blades around Nakime's neck, sawing rapidly back and forth.
Seeing Nakime's neck already halfway severed, the three's hearts surged with adrenaline and triumph.
"We did it!"
But before Inosuke could finish the cut, Nakime let out a piercing, bone-shattering scream.
The shriek ruptured their eardrums—blood began to trickle from their ears.
The scream echoed through the castle, reaching Doma, Hantengu, and every fighter still locked in battle.
Shinobu Kocho's eyes widened.
"It sounds like Nakime's been slain—Tanjiro and the others did it!"
Cheers rose among the Demon Slayers. Without Nakime's interference, they would finally fight on even ground.
But Doma hid his mouth behind his fan and sneered.
"So even with her guard up, she got caught off guard… Nakime really is useless. But—"
his eyes gleamed with amusement,
"the Nakime of now isn't the weakling she once was. After receiving Muzan-sama's blood, the power she gained… even I find it unsettling."
As if to prove his words true, a wave of force exploded from Nakime's chamber.
Tanjiro, Zenitsu, and Inosuke were hurled backward by a violent sonic blast.
Before their eyes, Nakime's half-severed neck regenerated instantly. The musical tones that once came from her biwa now resonated directly from her throat.
With each syllable she uttered, the castle itself moved—
the ceiling came crashing down, burying the trio beneath.
Tanjiro's concealment talisman fell from his forehead, fluttering to the ground as his body became visible again.
"Hinokami Kagura: Burning Sun Mirror!"
He slashed upward in mirrored arcs of flame, obliterating the collapsing ceiling.
"Thunder Breathing, First Form: Thunderclap and Flash!"
"Beast Breathing, Eighth Fang: Explosive Rush!"
Zenitsu and Inosuke charged forward together.
But before they could close the distance, Nakime's voice rang out again—
and suddenly, Zenitsu and Inosuke were frozen in midair, bound by invisible shackles.
Her single eye gleamed with cold fury, filling the room with murderous intent.
Another note escaped her lips.
From the walls, two sharp wooden spikes shot forth, aiming directly for the immobilized Zenitsu and Inosuke's heads.
Just as the spikes were about to strike—
"Hinokami Kagura: Circular Dance — Flash!"
Tanjiro burst forward in a blaze of fire, ramming both of them aside just in time.
Even so, they weren't completely unharmed—
the spikes tore into Tanjiro's shoulder, Inosuke's arm, and Zenitsu's leg, blood gushing from the wounds.
Grimacing through the pain, the three pulled the spikes free and used their breathing techniques to staunch the bleeding.
Nakime's biwa—her medium for controlling the entire Infinite Castle—had been destroyed.
Unable to manipulate the structure any longer, she chose instead to retreat and regroup with Doma and Hantengu.
The three of them—Nakime, Doma, and Hantengu—now gathered, revealing the monstrous forms born from the new powers granted by Muzan's blood.
Their combined aura surged, shaking the castle itself.
"Blood Demon Art — Heavenly Sovereign: Gandharva!"
From Nakime's single eye poured streams of blood, which condensed into a crimson biwa covered in countless blinking eyes.
"Blood Demon Art — Eternal Lotus Bloom!"
An enormous lotus of crystalline ice unfurled beneath Doma, who sat cross-legged upon it, forming a hand seal. A radiant Buddha phantom appeared behind him, holy and terrifying all at once.
"Blood Demon Art — Manifestation: Great Brahma Heaven!"
Hantengu's furious emotion clones remerged into his body, his form mutating until he bore six heads and twelve arms.
The overwhelming power radiating from their new forms filled everyone present with dread.