The battle raged on.
"Stone Breathing, First Form: Serpentinite Bipolar!"
With a mighty swing, Gyomei Himejima cleared another wave of demons, his expression grim and resolute as he pressed forward with urgency. He had to reach that place while Kibutsuji Muzan was still recovering.
Had Muzan given all these demons power equivalent to Lower Moons?
From the constant fighting along the way, Gyomei could sense that these demons were unusually strong. However, their movements were awkward, uncoordinated—as if their bodies hadn't fully adapted to the sudden increase in power.
"Grahhhh!"
"Raaaahhh!"
"Immediate regroup! Immediate regroup!"
Messenger crows shrieked as they soared frantically through the air.
The terrain of the Infinity Castle was being rapidly mapped and relayed. This was the handiwork of the eight-year-old Kiriya Ubuyashiki, the newly appointed head of the Demon Slayer Corps by his father. It was under his command that the final decisive battle against Muzan was now unfolding.
"Muzan-sama, I will divert them," came a voice.
The barbed thorns injected into Muzan's body earlier were laced with a unique compound—fruit of the joint research by Shinobu Kocho and Tamayo. It had the dual effect of forcing Muzan's form toward humanity and poisoning him with a concentrated Wisteria blend.
The toxins churned inside him, eating away at his cells. Muzan desperately needed time to purge the poison.
"Yes, my lord!"
Nestled at the very heart of the Infinity Castle, Nakime—the Biwa Woman—sensed all that transpired within. Her long, clawed fingers danced wildly across the strings of her instrument, shifting the structure of the Infinity Castle itself to hinder the Hashira.
"Once Lord Muzan recovers, all these fools will die."
Suddenly—
"So it's you... the one controlling everything."
Two figures emerged from the shadows—Sound Hashira Tengen Uzui and Wind Hashira Sanemi Shinazugawa.
The two fastest among the Hashira, they darted through the warped corridors with blinding speed, expecting to face Muzan himself. Instead, they found Nakime calmly seated before them, Biwa resting in her lap.
Two enormous buildings rose instantly between them, blocking their path.
"Damn it!" Sanemi cursed, forced to alter his trajectory. Both Hashira redirected toward the center.
If they wanted to find Muzan, they had to eliminate the one pulling the strings first.
Elsewhere in the castle—
The remaining Hashira were also under siege by hordes of demons. Though such enemies were nothing to fear individually, their overwhelming numbers made things difficult.
Muzan had distributed vast quantities of his own blood to the demons. Many who couldn't withstand it had died, their bodies bursting from within. But a far greater number had survived and grown monstrously powerful—no longer demons, but beasts driven by sheer bloodlust.
"Damn it, there's just too many of them!"
Serpent Breathing, Fourth Form: Twin-Headed Reptile!
Iguro Obanai moved with the sinuous grace of a snake, his slashes fluid and deadly. Another cluster of demons fell beneath his blade.
The earlier annihilation of nearly all Upper Moons had cost Muzan a significant portion of his elite force. Now, these demons served merely to delay the Hashira.
Creating a new Upper Moon wasn't simply a matter of pouring blood—it required potential, and most importantly, the ability to withstand Muzan's blood. Muzan, in his desperation, had forcefully given his blood to all the demons. Those unworthy had already perished.
To the ordinary Demon Slayer Corps members, these demons were overwhelming. Even the Hashira were being slowed, their progress hindered step by step.
"You filthy things—go die for me!"
In a secluded room of the Infinity Castle, two Demon Slayers were strangled to death by a whip-like sash.
Daki.
She had long been waiting here.
"Big brother, you'll protect me, won't you?" she murmured, almost to herself. Even she knew—this was the final battle. Beautiful and vain, Daki didn't want to die like this.
"To your left!"
A voice echoed in her mind. Daki swiftly dodged.
"So you're the last of the Upper Moons? You deserve to die."
Tears streamed down Gyomei Himejima's face. The image of his comrades being strangled enraged him.
"Well, well, if it isn't the stinking monk," Daki sneered, eyeing Gyomei's massive frame and the iron chains he wielded. "You're uglier than I imagined."
"Die!"
"Damn it! This demon's a pain in the ass!"
Once again blocked by a shifting building, Sanemi's scarred face twisted with fury. He'd been trapped repeatedly, and it was driving him mad.
"We need a way to reach her!"
Tengen, on the other hand, remained calm. He understood that the Biwa Woman was the puppet master of this place—kill her, and Muzan would lose his greatest advantage.
Nakime's fingers danced once more across the strings, shifting the entire layout of the Infinity Castle. The changes didn't just affect the two Hashira in front of her—every corridor, every chamber shifted, throwing the entire Demon Slayer Corps into disarray.
Water Breathing, Tenth Form: Constant Flux!
The Nichirin blade carved a flawless arc through the air, slipping through collapsing rooms with the elegance of a stream.
A young man with jet-black hair arrived.
Water Hashira, Giyu Tomioka, had made it.
Nakime hastily erected a barrier between them, panic flashing in her eyes.
"Now's our chance!"
Tengen and Sanemi, sensing the disturbance in her rhythm, launched themselves forward, blades raised.
….
"Brother!"
"Help me!"
Daki's scream echoed. The monk was too strong. She barely evaded his flail, and now she was on the verge of collapse.
"Shut up already! Leave it to me!"
From within Daki's body, Gyutaro emerged.
"Anyone who dares hurt my little sister... dies!"
Under Gyutaro's control, Daki lunged once more at the Stone Hashira.
"It's almost over, you wretched Tamayo."
Muzan's body rapidly decomposed the toxins within. Bit by bit, he was recovering.
Once he was whole again, and with the terrain under his control, Muzan would annihilate every last Demon Slayer here tonight.
He was sick of this existence. These ants, always crawling back to resist him, were obstacles in his path to eternity.
BOOM!
His balance faltered. Muzan reached out, bracing himself against the wall.
"Nakime!"
The report hit him—she was dead.
With her demise, the twisted halls of the Infinity Castle began to collapse, revealing the true battlefield—open and unshielded.
"Useless garbage. Every last one of them!"
BAM!
A figure crashed into him before he could react. Muzan's arm shattered on impact.
Golden wings flared—Yohan had arrived, bringing the Ubuyashiki siblings to the Butterfly Estate.
"Muzan!"
"Yohan!"
Muzan locked eyes with the man before him. It was their first face-to-face encounter, yet this face had haunted his mind for what felt like an eternity.
"So, it's come to this at last, Muzan."
Yohan's gaze was steady, almost wistful. He recalled the tragic end of his previous life, where even with everyone's combined strength, Muzan had barely been killed. But this time, things could change.
This time, he could bring hope to this world.
"Why not join me?" Muzan suddenly asked.
He wasn't stupid—he had once built the Twelve Kizuki for a reason. And now, with Yohan standing before him, his immense vitality was undeniable. Muzan could feel it in his bones.
"Become a demon. I'll make you the strongest of them all—above even the Upper Moons. You'll serve directly under me."
It wasn't just Yohan's power Muzan wanted—he also sensed his connection to Tamayo. If Yohan turned, then Tamayo would follow.
"Hahahahaha..."
Yohan laughed aloud.
"What's so funny?!" Muzan snarled, insulted by the mockery. Did this insect really think he couldn't be killed?
"I'm laughing... because you're already dead!"
Eyes blazing, Yohan hurled a devastating punch straight at Muzan.