Kapitel 18: The Calm Before the Storm – The Fall to Infinity Castle

Six months had passed since the Mugen Train mission. In that time, the Demon Slayer Corps had trained relentlessly, especially the six new Hashira—Tanjirō, Inosuke, Zenitsu, Kanao, Genya, and Senjurō. Each of them manifested their Demon Slayer Marks, but more importantly, they learned to stabilize them, channeling the power through grueling combat training from the Dragons. Their combat prowess had sharpened to deadly precision, their teamwork flawless.

But while they were becoming stronger, the enemy was growing restless.

Muzan's Growing Frustration

Far away, in the eerie chambers of the Infinity Castle, Muzan Kibutsuji was livid. His piercing red eyes burned with unbridled rage as he sat upon his throne, his long, slender fingers drumming against the armrests. His informant, Akaza, had delivered news that sent waves of euphoria through Muzan's twisted heart—the blue spider lily was rumored to be at the Demon Slayer HQ. For centuries, Muzan had searched for this fabled flower, which he believed held the key to perfecting his immortality.

Now, after all this time, he finally had a lead.

Muzan wasted no time. He summoned his Lower Ranks and Upper Moons to the Infinity Castle, their forms materializing in the vast, ever-shifting space. The atmosphere was tense, the demons standing at attention as Muzan's cold, calculating gaze swept over them.

Standing closest to Muzan was Kokushibo, the Upper Moon One. His six menacing eyes radiated a terrifying calm. As Muzan's right hand, Kokushibo commanded immense respect, even from the other Upper Moons. His samurai-like appearance, combined with his vast knowledge of swordsmanship, made him a living nightmare for any Demon Slayer. Beside him, the chaotic aura of Doma, the Upper Moon Two, was a stark contrast. Doma's unsettlingly serene smile never wavered, his golden eyes twinkling with a sadistic glee. His personality—both charming and grotesque—matched his deadly cryokinesis and spiritual absorption.

Akaza, the Upper Moon Three, stood confidently next to Doma, though his gaze was far less cheerful. Akaza's immense power came from his martial arts, and his thirst for battle was insatiable. The mere mention of combat made his blood boil with excitement, but his hatred for the weak disgusted him even more.

Further back, the disturbing and snake-like Hantengu, Upper Moon Four, cowered slightly, his cowardly disposition hiding his true strength—his ability to split his emotions into different entities, each a monstrous fighter in its own right. Hantengu's multiple personalities always made him unpredictable, and that unpredictability had proven fatal to his enemies many times over.

At the edge of the room, Gyokko, Upper Moon Five, twisted his grotesque form, his pot-like body pulsing with anticipation. His obsession with creating "art" through the bodies of his victims had driven many to insanity before he even touched them. Gyokko's ability to manipulate his own body and summon deadly aquatic creatures added a dangerous layer to his already disturbing personality.

Finally, Gyutaro and Daki, Upper Moon Six, stood intertwined, their brother-sister dynamic feeding off one another's viciousness. Daki's beauty hid her cruelty, her sash-like obi weapons cutting down enemies with grace. Gyutaro, with his sickle-like weapons and overwhelming jealousy, completed the pair, making them a force that could bring ruin to any Demon Slayer.

"Find the Blue Lily"

Muzan's icy voice cut through the silence, demanding the demons' full attention. "The time has come," he began, his tone sharp and authoritative. "Find the Demon Slayer Headquarters. Lower Ranks, scour the land. Tear apart every stronghold, search every village. I want the blue lily, and I want the location of the HQ."

The Lower Moons, trembling in fear, bowed deeply before vanishing into the shadows, knowing full well the price of failure.

Muzan turned his attention to the Upper Moons, his most powerful lieutenants. "Prepare yourselves for battle. The moment the HQ is found, you will lead the assault. I want every last slayer wiped out."

The Upper Moons grinned in unison, their malevolent anticipation thick in the air.

But as Muzan plotted, little did he know that the MC had already anticipated this move. His shadow agents—a secret network of spies loyal only to him—had been feeding false information to the Lower Moons for months, sending them on wild goose chases across the land. As a result, the Demon Slayer Corps had remained hidden, giving them the precious time they needed to train and prepare for the coming war.

The Silent Six Months

The six Hashira trained relentlessly. Each day was spent perfecting their breathing techniques, mastering their swordsmanship, and learning from the Dragons. The MC's watchful eyes were always on them, silently guiding their progress.

Tanjirō, now the Sun Hashira, honed his Hinokami Kagura to new heights, each movement a perfect blend of fire and precision. Inosuke, the Berserk Dragon, pushed his body to its limits, his raw strength and agility becoming terrifyingly powerful. Zenitsu, the Thunder Hashira, continued to perfect his Thunder Breathing forms, his lightning-fast strikes becoming deadly accurate. Kanao, Genya, and Senjurō also showed remarkable progress, their skills complementing their peers as they grew into their roles.

But something more was brewing behind the scenes. The MC had forbidden the Dragons from killing the Upper Moons when they encountered them, instructing them instead to push the demons back without delivering a fatal blow. This directive puzzled many of the Dragons and Hashira alike. Why hold back when they had the chance to eliminate such powerful enemies?

Some Dragons, particularly the more aggressive ones, grumbled about the order, their instincts urging them to finish the demons off. But they trusted the MC's wisdom, knowing he always had a reason.

Another six months passed, and the time finally came to set the stage.

The Bait is Set

The MC's shadow agents had fed the ultimate piece of false information to Muzan's network—the true location of the Demon Slayer HQ. Muzan took the bait, believing the time had come to strike a fatal blow against the Corps. His fury had grown uncontrollable after months of fruitless searching, and now he was ready to act with devastating force.

He prepared to lead the assault himself, a rare move for the Demon King. With his Upper Moons by his side, he was confident that the Demon Slayer Corps would fall, and the blue lily would finally be his.

On the day of the assault, Muzan arrived at the supposed HQ with an air of supreme arrogance. His every step was measured, his posture regal, as if he was already the victor. His presence was so overwhelming that the very air seemed to distort around him, and the ground trembled under his feet.

As he entered the heart of the HQ, he was greeted not by the Boss, but by the MC, standing alone at the center of the hall.

The MC smiled, a dark glint in his eyes as he casually rose from his seat and began to approach Muzan, his movements deliberate and calm. "You're early, Muzan," he said, his voice steady, carrying a tone of amusement.

Muzan's eyes narrowed, but his body remained poised, ready for battle. "Where is your master?" he asked coldly, his voice dripping with malice. "I've come to end this farce."

The MC's smirk deepened. "You'll find that plans don't always go the way you want them to."

Before Muzan could react, a blur of motion sliced through the air, too swift to track. Tengen, the Silent Dragon, appeared from the shadows, his movements eerily quiet. In one swift motion, he jammed a syringe into Muzan's neck, the needle plunging deep into his skin.

Muzan let out a snarl of pain as the serum entered his bloodstream. He staggered, his hand instinctively moving to swat Tengen away, but the Sound Hashira had already disappeared into the shadows, just as swiftly as he had arrived.

The Demon King fell to his knees, the pain coursing through his veins like molten fire. His regeneration powers were stunted, his body convulsing as it struggled to adapt to the serum.

"What... have you done to me?!" Muzan roared, his voice strained, his usual calm shattered by the unexpected agony.

The MC, still calm, folded his arms and smiled down at Muzan. "A little something I cooked up with Tamayo-san. It won't kill you, but it'll stop you from splitting into pieces and running away. Call it... a handicap."

Muzan's eyes blazed with fury. "You think this will stop me?!" he snarled. "I will crush every last one of you!"

Before the MC could respond, Muzan's lips curled into a malicious smile. "I think it's time for a little... change of scenery."

Suddenly, doors—massive, black, and ominous—materialized beneath every Hashira, every Dragon, and every agent within the HQ. They barely had time to react before the ground gave way beneath their feet, and they were swallowed by the gaping void.