Demon Slayer: Battle of the Infinite Castle
As Doma and Hantengu's clones joined the battlefield, death and destruction spread wherever they passed.
At the Ubuyashiki estate, Kagaya Ubuyashiki, calmly directing from his residence, fully understood that any Demon Slayer whose strength had not yet reached the level of a Hashira would be of no use in a battle against the Upper Moons — joining the fray would only mean meaningless sacrifice, and would even hinder the Hashira from fighting at full strength.
Kagaya immediately issued his command:
"All Demon Slayers below the Hashira rank — focus on holding back the demon army. Clear the battlefield and create space for the Hashira to fight freely! Tanjiro, Zenitsu, Inosuke, and Genya Shinazugawa — you are to stay and assist the Hashira in their battles!"
Following the order, the swordsmen of the Demon Slayer Corps, drenched in blood yet unyielding, began pushing back the enemy lines. After fierce and relentless effort, they finally cleared an open space on the battlefield large enough for the Hashira to unleash their full power.
Only a few scattered demons remained. The Hashira swiftly cooperated to slay them, and at last, they stood face to face with Doma, Hantengu, and Muzan Kibutsuji himself.
"Everyone, be careful," warned Kokushibo — once known as Upper Moon One, now standing with the Demon Slayers as Michikatsu Tsugikuni. "The Doma and Hantengu before us are not as they once were. It's highly likely they've both received more of Muzan Kibutsuji's blood and survived the process. Their current strength has reached, or perhaps even surpassed, what mine once was as an Upper Moon."
The hot-tempered Sanemi Shinazugawa snarled, his bloodshot eyes blazing.
"I don't care how strong they are. We just have to kill them!"
"Wind Breathing, Third Form: Clean Storm Wind Tree!"
Sanemi was the first to move — in an instant, three massive wind blades shot out from his position, aimed at Doma, Hantengu, and Muzan simultaneously.
"Blood Demon Art: Freezing White Princesses!"
Doma swung his twin fans. Empowered by Muzan's blood, his Blood Demon Art now produced nine ice maidens instead of the usual few — all in the form of lotus-like women exhaling freezing mist that spread across the battlefield, freezing Sanemi's wind blades mid-air and rapidly expanding outward.
Muichiro Tokito and Kokushibo exchanged a brief look before stepping forward together.
"Moon Breathing, Ninth Form: Waning Moons – Swaths!"
Their Nichirin blades danced in overlapping arcs, releasing countless intersecting, invisible slashes of moonlight. The chaotic web of blade winds sealed off the freezing mist completely.
Meanwhile, Hantengu's clones merged together, forming his most powerful manifestation — Zohakuten.
"Blood Demon Art: Furious Crying Thunder Drums!"
Zohakuten struck the drums on his back, unleashing destructive shockwaves that tore through the ground.
"Water Breathing, Eleventh Form: Dead Calm."
Giyu Tomioka entered a state of serene stillness, nullifying every one of Zohakuten's shockwaves within his blade's reach. His tranquil domain rendered all incoming techniques ineffective — a perfect opening for the Hashira to counterattack.
Seizing the moment, Gyomei Himejima, the mightiest of the Hashira, leapt high into the air.
"Stone Breathing, Fifth Form: Arcs of Justice!"
He hurled his axe at Doma's ice maidens, then his flail at Zohakuten, alternating his weapons in devastating rhythm. Each strike shattered the earth and crushed everything in its path.
In a single instant, all of Doma's ice maidens were obliterated.
But Zohakuten could not be killed so easily — as a clone, he could regenerate endlessly even after decapitation. Though his body was smashed to pulp by Gyomei's blows, he quickly reformed in the center of the battlefield.
At the moment Zohakuten's body reconstituted, Mitsuri Kanroji darted forward like a swift cat, her movements a blur. She recalled Kokushibo's warning — to kill Hantengu, they must strike his true body.
Though she appeared to be rushing at Zohakuten, her real target was Hantengu himself.
Just as Zohakuten raised his drums to attack, Mitsuri feinted and charged straight for the hidden body.
"Love Breathing, Second Form: Love Pangs!"
She spun forward with lightning speed, swinging her whip-like blade in a flurry of beautiful, arcing strikes aimed at Hantengu's true form.
Sensing danger to its core, Zohakuten moved faster than Mitsuri — positioning himself between her and Hantengu.
"Get lost, you shameless woman! Blood Demon Art: Crushing Roar!"
He struck his drums again, unleashing a massive soundwave that blasted Mitsuri high into the air.
In an instant, another drumbeat echoed — a massive wooden dragon manifested and lunged upward, jaws wide open, ready to devour her.
"Serpent Breathing, First Form: Winding Slash!"
Obanai Iguro leapt into the air, catching Mitsuri in his arms mid-flight. Spinning his body counterclockwise, he slashed in a graceful, serpentine arc, slicing the wooden dragon clean in two before landing back among the Hashira.
Mitsuri's cheeks flushed red, but she had no time to thank Obanai — her mind still lingered on what Zohakuten had just called her.
"A... a shameless woman?! Was he talking about me?!"
Fuming, she protested aloud, "Unbelievable! What kind of thing talks like that?! He looks barely older than my little brother... Ah! But I suppose demons' ages don't match their looks — still, that's so rude!"
Meanwhile, deep within the Infinite Castle, Akaza and Gyutaro wandered aimlessly through the labyrinthine halls.
The outside world was roaring with battle, but within the castle — an eerie silence.
Each time they opened a door and advanced further in, the same sound would echo — the plucking of a biwa string — and in an instant, they would find themselves back where they started.
Gyutaro scowled. "Damn it! Hakuji-san, it looks like we won't find Yōsuke-sama unless we deal with that biwa woman first."
Hakuji's expression darkened. "Agreed. If we keep going like this, we'll never reach him."
It sounded simple — but in reality, it wasn't. They didn't know where Nakime, the Biwa Demon, was hiding. Even if they did, her Blood Demon Art allowed her to reshape the very structure of the Infinite Castle at will, endlessly toying with them.
Then, suddenly, Hakuji's eyes lit up. "I've got it!"
Gyutaro turned to him. "What is it?"
Hakuji explained, "All demons give off fighting spirit. My Compass Needle can sense it. If that woman uses her Blood Demon Art, her fighting spirit will flare — and the Compass Needle will react to it."
"Got it," Gyutaro said, nodding. "I'll keep pushing forward. As soon as she moves, you'll sense her, right?"
Hakuji nodded firmly. "Exactly."
As Gyutaro disappeared down the endless corridor, Hakuji closed his eyes and exhaled deeply.
"Technique Deployment — Destructive Death: Compass Needle!"
A twelve-pointed snowflake sigil bloomed beneath his feet. Standing within it, Hakuji waited silently, focusing every sense for the sound of that biwa's next note...