{[AUTHORE NOTE--Chapters 13 & 14 served as a flashback to events that occurred prior to the present storyline. They covered key moments such as Alex's growing romantic bond with both Cara and Shinobu, as well as the strategic planning to bait Muzan and counter any potential ambushes from him.
Please remember—this is not an anime adaptation. In this version of the story, Muzan is terrified of Alex. Unlike in canon where he only feared Yoriichi, here he's even more cautious, because he can feel that Alex far surpasses Yoriichi's strength. Alex isn't someone he can afford to underestimate.
Now, regarding the upcoming fight: Alex will face Muzan, but don't expect a long, drawn-out battle. Alex is overwhelmingly powerful in this verse, and he never holds back when facing someone he intends to kill. That means the battle will be intense but short. However, don't worry—the upcoming fight chapters will still focus heavily on the Demon Slayer characters and showcase their struggles, powers, and development.
Now sit back and enjoy the chapter!}]
INFINITY CASTLE - PRESENT
third person pov
All the Upper Moons were now stationed at their designated locations, their presence saturating the air with dread.
Countless lesser demons slithered and crawled through the twisted corridors of the Infinity Castle, their grotesque forms blending into the warped architecture.
At the heart of this chaotic fortress stood Muzan Kibutsuji, his pale, expressionless face lit by the eerie glow of the castle walls.
Beside him was Nakime, the biwa player whose every note could reshape the castle itself like clay in her hands.
"Nakime, are you ready?" Muzan's voice slithered with disdain and arrogance, devoid of empathy. "Just bring all those insects here."
To him, the lives of humans—and even demons—meant nothing more than dust beneath his feet.
Nakime, her face partially obscured by shadows and her long black hair, responded without raising her gaze. Her fingers gently plucked the strings of her biwa, sending subtle vibrations through the air.
"Muzan-sama… I can do that," she said in her calm, hollow voice. "But I cannot sense the girl you spoke of. Moreover, there's something strange—a mark has appeared on each Demon Slayer. It feels… unnatural. It might be the doing of that person."(Flying ryjin mark)
Muzan's crimson eyes narrowed, a flicker of rage cutting through his composed façade.
The very mention of him—the man who dared interfere—filled him with loathing. If it weren't for Nezuko, he would never have considered leaving this place. He still didn't know when—or if—another demon capable of walking in the sunlight would ever be born.
And now, someone had made it happen.
"Then we proceed with the plan to divert his attention," Muzan growled, his tone sharp with fury. "We'll send out the Upper Moon who has accomplished nothing for a century… and yet this stranger appears and effortlessly creates a demon immune to sunlight. Just like that."
His anger was palpable, simmering beneath his words like a volcano waiting to erupt.
'Muzan-sama is angry…' thought Upper Rank Four, cowering behind the staircase. He dared not speak, dared not move, for fear that Muzan's wrath might turn on him next.
Then, with a graceful swirl of frost-kissed air and a fan that shimmered with every color of a dying sunset, Dōma, the Upper-Rank Two, appeared.
"Oya oya~ such excitement tonight, Muzan-sama," he said with a wide, unsettling grin, clasping his hands as if in prayer. His multicolored eyes sparkled with wicked amusement, unfazed by the tension in the air.
"Shall I offer them a proper welcome?"
His voice was honeyed and soft—yet beneath it lurked a sadistic hunger.
Muzan's gaze shifted, dispassionate and razor-sharp, locking onto Dōma.
"You talk big for someone who has never killed a single Hashira—except for the female one," Muzan said coldly, his tone laced with scorn.
His crimson eyes gleamed with a contemptuous glint, making even the ever-smiling Dōma flinch internally.
For a moment, Dōma's grin faltered, though he quickly recovered with a chuckle, fanning himself as though Muzan's words were nothing more than idle wind.
"Oya~ such harsh words, Muzan-sama. But if you insist, I shall redeem myself in a most exquisite fashion."
Before the tension could rise further, Kokushibo, the Upper-Rank One, stepped forward from the shadows.
His presence was heavy—imposing like a mountain, silent and commanding respect. His six eyes remained fixed on Muzan, unwavering.
"Muzan-sama, though we have failed to fulfill your purpose thus far, rest assured…" Kokushibo said, his voice deep and composed, like tempered steel.
"We will carry out your will. As for that man who inherited the Sun Breathing art… I will be the one to put an end to him. Once more."
Muzan remained silent for a moment, studying the swordsman who had once been Yoriichi's brother—a man so devoted he would slay even his own kin at Muzan's behest.
Among his subordinates, Muzan only truly trusted his three slaves:
Kokushibo, the blade that severed bloodlines.
Akaza, his loyal errand runner, is ever-eager to please.alas he died.
And Nakime, the silent musician whose biwa carved out a sanctuary of illusion and safety for Muzan to hide in—no, reside in.
He would never admit it aloud.
"Then we'll proceed with a two-pronged plan," Muzan declared, turning away as his cape fluttered with a whisper. "Nakime—transport half of those insects here into the castle. Let them drown in this cursed maze."
Name nodded, her fingers already brushing the biwa strings.
"As for the rest—" Muzan's gaze flicked over the gathered demons like a butcher inspecting meat.
"Dōma. Hantengu. Daki. Gyutaro. You four will lead a demon force and begin a purge. Wipe out every village in the surrounding regions. Leave no soul breathing. Slaughter everyone on sight."
His voice turned venomous as he added, "And if you encounter a Slayer named Alex… do not fight him. Stall him. Keep him occupied. I will deal with him myself—once I obtain the girl."
A bitter irony, though Muzan didn't know it.
Nezuko, the girl he so desperately sought, was not even on this plane. She resided safely within the System Space, protected alongside Tomoya and her loyal subordinates.
And Muzan, so proud and all-knowing, had no idea he was already too late.
Then it happened.
A sharp, twang—the sound of a biwa string being plucked—echoed through the void like a curse. It rang once, and in an instant, the air cracked apart like shattering glass.
Twang…
All the demons previously assigned—Dōma, Hantengu, Daki, Gyutaro—along with hordes of lesser demons, vanished in a flash of dark energy and teleported outside the castle.
They descended upon surrounding villages with monstrous hunger, beginning the slaughter without hesitation. Not a single flinch. Not a shred of mercy. Screams erupted like wildfire in the night.
And then,5 minutes later—
Twang…
Another ripple in reality, another pluck of the cursed biwa.
This time, it wasn't demons who vanished. Half of the Demon Slayer Corps was forcefully wrenched from the world above and pulled into the nightmarish maze known as the Infinity Castle.
Among those trapped inside were the strongest remaining forces:
Gyomei Himejima, the Stone Hashira.
Sanemi Shinazugawa, the Wind Hashira.
Giyu Tomioka, the Water Hashira.
Iguro Obanai, the Snake Hashira.
Tanjiro Kamado, Zenitsu Agatsuma, and the masters—Jigoro Kuwajima, Urokodaki Sakonji, and Shinjuro Rengoku, father of the Flame Hashira.
As Tanjiro tumbled through the spatial rift, his eyes widened in horror and falling down in mid air,along with giyu.
The scent—thick, iron-heavy, and suffocating—choked his lungs. The stench of countless demons clung to the walls like rot.
His vision twisted.
The sky above became a ceiling below. Corridors spiraled into nothingness. Stairs looped like serpents. It was as if the laws of gravity themselves had collapsed. They were inside a living nightmare, a dimension that pulsed with malevolence.
The Infinity Castle.
Tanjiro's boots hit the solid ground—but the earth beneath him felt wrong like he was standing on the ribs of some vast creature. He steadied himself, chest heaving.
Then he saw him.
Muzan Kibutsuji.
Still. Silent. Terrifying in his calm.
Pale as bone. Eyes burning a cruel crimson. Standing with quiet arrogance at the heart of the shifting chaos, as if he were its god.
Tanjiro froze for a heartbeat—but only a heartbeat. His grip tightened around his sword, and the fire in his chest surged into a roar.
"MUZAN KIBUTSUJI!!!" he shouted, the words tearing from his throat like thunder.
His voice cracked through the walls of the Infinity Castle, slicing through distorted ceilings and endless stairs, shaking the very fabric of this realm.
"You've taken so many lives! You've destroyed so many families! You've escaped justice for over a thousand years…But it ends here! Right now! I swear on every soul you've taken-
I'LL BE THE ONE TO END YOU!!"
His voice echoed with unyielding fury, the spirit of every fallen warrior screaming with him.
Muzan's eyes shifted slightly, his expression cold—unchanged. There was no fear in his gaze. Only loathing, like a king looking down on a starving dog.
Unlike in original he didn't even bother to answer that rage towards him he just scoffed.
But Tanjiro's fury had pierced the dark heart of this place. And all the other demon slayers smiled.
And with that cry, the battle had begun.
`````````````
UKNOWN VILLAGE - WHERE DEMONS WERE TRANSPORTED
third person pov
Laughter echoed across the blood-soaked streets.
"Hehehe… Muzan-sama will embrace me again if I do this job perfectly…"
Daki's voice was light, almost dreamy as if she were talking about a lover's praise rather than a massacre.
Her eyes sparkled with deranged joy as her blade-like obi cleaved through screaming villagers—heads flying, bodies crumpling before they could even beg for mercy.
Blood sprayed across her flowing kimono, painting the delicate fabric a deep, sticky crimson.
"Tch… these insects," she muttered in disgust, planting her foot down on one of the corpses.
Crunch.
Then again.
Crack.
And again.
Splat.
A sickening rhythm of violence as she kicked the mutilated body into a pulp. The sound of meat being minced filled the air.
Splash. Splash.
Her footfalls through pools of blood echoed like soft drums of death.
"Daki…" came a voice beside her.
Gyutaro slithered into view, his skeletal frame hunched, eyes twitching as he looked around the burning village.
His blades dripped with fresh blood, but his tone carried a hint of caution.
"Don't get so riled up it doesn't suit you."he said.
Daki glanced at her brother, flicking a lock of blood-matted hair behind her ear.
"Oni-chan, don't tell me what to do. Do you really think these pests matter? Whether they die in groups or one by one—they're still just vermin. Worthless. Squirming. Disgusting."
She leaped onto a rooftop in a swirl of silks and death, her obi lashes extending out like hungry serpents.
With a graceful twist, she tore through the house below, collapsing it in a flash of carnage and screams.
Gyutaro stayed behind for a moment, staring at the mangled body of a woman sprawled on the ground.
Blood oozed from her gaping wounds, but it wasn't her that caught his eye—it was the two children, a boy and girl, the boy clinging to her even in death.
Their tiny arms wrapped around their mother, their lifeless eyes still wide with terror.
Something flickered in Gyutaro's gaze. A ghost of an old pain. A memory.
"Ala~ my ugly Gyu," came a singsong voice from behind, mocking and cold.
Dōma appeared, twirling a severed head in one hand like a toy. The female head was still fresh, her eyes frozen in fear. Blood dripped down Dōma's chin, his beautiful face smiling far too widely.
"Why so quiet? Not showing the same enthusiasm as your dear sister? Hmm~? If she were human, maybe I'd—"
Clang!
Gyutaro was in front of him in an instant. His sickle clashed against Dōma's closed fan—a single inch away from slicing Dōma's throat. The air cracked from the force of it.
"Don't say one more word about my sister… with your filthy mouth."
His voice was pure venom, his twisted frame trembling with barely contained rage.
Then he vanished in a flicker of shadows, leaping into the massacre below with savage fury—slaughtering everything in sight.
Dōma blinked. Then chuckled.
"Well… that was rude," he murmured, licking a drop of blood from his thumb. His rainbow eyes sparkled with mischief and madness.
"Why don't we continue this dance then, shall we?"
He turned his gaze toward a distant village still untouched—
Just as Dōma prepared to leap backward, he froze.
That presence—the weight of a Demon Slayer's intent—washed over him like a crashing tide.
His rainbow-colored eyes flicked to the side.
Muichirō with him love hashira also followed.
The Mist Hashira passed by him in a blur, not sparing even a glance. Not even acknowledging Dōma's existence.
He leaped silently from rooftop to rooftop, his blade drawn—not for Dōma, but for Upper Moon Four. Following Shinobu's orders.
At the same time, Tengen Uzui found himself face to face with Gyutaro, blades gleaming, a grin twitching on his lips.
And Rengoku to fulfill his utmost duty assigned by his mother 'protect the weak'—saw Daki, her blood-drenched kimono fluttering as she butchered children with the same ease as swatting flies.
He charged toward her, eyes burning.
But Dōma?
He ignored them all.
His eyes had locked onto a single person.
Shinobu.
She stood calm and poised, yet ready for war.
Beside her stood, Alex,
Kanao, silent but alert, and
Inosuke, twitching with anticipation like a beast barely held back by instinct.
Dōma's lips parted. His voice oozed with faux wonder—dripping with something far more grotesque.
"Ahhhhhh… so beautiful. So elegant. So… full of life."
He moaned the words as if the sight alone gave him an orgasm.
Alex's eye twitched. His mouth curled downward in visible disgust.
"So it's you," Shinobu said softly, her tone calm—but carrying a blade beneath each syllable.
Her violet eyes never left him. "Upper Rank Two. Dōma."unlike before she knows him too well now because of simulation training.
She didn't draw her sword yet.
Dōma stood, gently placing the head down like a porcelain doll.
"Yes, yes! That's me." He tilted his head.
"And you… you're the Insect Hashira. Shinobu Kocho. I've heard about you. Such a cute little thing. So elegant. So poisonous."
He chuckled, eyes gleaming like frost.
"Are you here to avenge that Kanae girl? Your sister, right?"
Shinobu's breath hitched—but her face remained impassive.
"You remember her?"
"Oh, of course, I do," Dōma smiled wider, oblivious to—or perhaps enjoying—the dagger in his words. "She was so strong. So full of life. Her final moments were… exquisite."
A crack appeared in Shinobu's calm.
Her fingers curled around the hilt of her blade.
"I see," she whispered. "Then there's no need for words."
"Mm?" Dōma blinked. "Why not talk a little? Don't rush. You have such a lovely voice. And I really do enjoy conversations before dinner."
Her eyes narrowed.
"You're not going to eat me."
Dōma's expression flickered. Just a moment. Just a shift in the air.
"Oh? And why not?"
The air around them had grown thick. Not with fear—but with fury.
"Because I'm going to send you the place where shits like you deserve" she said her voice low and cold like steel drawn in moonlight.
"And because my lover will kill you before you even touch a single strand of my hair." She smiled.
But it wasn't a sweet smile.
It wasn't warm.
It was a curse—wearing lipstick.
A promise of death dressed in beauty.
Dōma blinked. Just once. His eternal grin remained—but something in his posture shifted. His smile froze a second too long.
"...Hah. That's so sad," he murmured with a soft, almost theatrical sigh. He didn't care about the death threat Shinobu said to him he was more interested in the "lover" word
"That such a beautiful flower already has a… caretaker."
A pause.
Then his lips curled up again—twisted, possessive, predatory.
"Well then… why don't I kill him first?" he whispered with deadly sweetness.
"And once he's gone, I'll love you… for all eternity,because you will be with me forever just like every flower i plucked who were full of life just like you heh"said with an innocent smile and eyes half closed with lust.
Shinobu's eyes narrowed.
And then—her blade flashed.
"I would rather burn myself than be touch by bastard like you."
Her voice hit like a slap of thunder. But before Dōma could blink—
Boom.Clink
a sound of sword sheathing was sounded
A pulse of pressure tore through the air. A flash of motion burst beside him.
And then—
"What was that you were saying… about my woman, you trash filth"
The voice was cold. Unmistakably calm.Too calm.
Dōma's instincts screamed.
He tried to leap back, to gain distance, but—
Gravity betrayed him.
His body felt weightless—unnaturally light as if the ground had disappeared beneath him.
Eyes wide, he glanced down. And saw them.
"kugh" he let out the voice as if his wounds are burning
Two severed legs. Still standing upright.
The raw, torn ends twitching from the sudden dismemberment. Dōma's own.
And beside them stood a man.
Alex.
He wasn't angry. He was smiling. And that smile… was death wrapped in charm.
He stepped forward
His voice dropped into a razor whisper:
"Don't fuck around"