Crimson Monarch: The Rise of Muzan Kibutsuji

As the Demon Slayer Corps

approached under the cover of night, their Nichirin blades gleaming faintly. Led by Shinjiro Hagane, the Steel Hashira, the slayers radiated a fierce determination. They had faced countless demons before, but the reports of the Demon Kings actions filled even the most seasoned warriors with unease. 

"Stay sharp," Shinjiro commanded, his blade resting on his shoulder. "This isn't a simple nest. We're walking into the lair of something far worse than any demon we've faced." 

Beside him, Kiyomi, the Azure Wind Hashira, tightened her grip on her twin blades. "The air reeks of death," she said. "This is no ordinary hunt." 

From the shadows of the fortress, Azara's serpents slithered forth, hissing and snapping as they swarmed toward the slayers. 

"They've spotted us!" shouted Daichi, the Crimson Fang Hashira. His crimson blade flared to life as he charged forward, slicing through the serpents with savage precision. 

Shinjiro and Kiyomi moved in unison, their blades cutting a path through the horde. The slayers advanced, their teamwork impeccable, but the deeper they pushed, the heavier the atmosphere grew. 

Azara's serpents retreated as the slayers breached the gates of the fortress. Inside, the air was thick with malice, and the faint sound of laughter echoed through the halls. 

Standing at the center of the chamber was Ethan Brook, his crimson eyes gleaming with amusement. Beside him stood Kyogan and Azara, their menacing forms radiating power. 

"Welcome, Demon Slayers," Ethan said, his voice calm but laced with venom. "I've been expecting you." 

"Enough talk," Daichi growled, pointing his blade at Ethan. "We're here to end you we will achieve what Yorrichi never managed to" 

Ethan smirked. "You're welcome to try." 

Immediately after Daichi launched himself at Ethan, his blade blazing with fiery energy. Ethan met his attack with ease, parrying with a blade formed from his own flesh. The impact shook the room, but Ethan remained unfazed. 

Shinjiro and Kiyomi joined the fray, their blades weaving deadly patterns. Kyogan stepped forward, his third eye glowing as he used his third eyee to predict their movements. With calculated strikes, he intercepted their attacks, forcing them to fight defensively. 

Azara unleashed her serpents, which coiled around the slayers, their venomous fangs snapping dangerously close. Kiyomi countered with her wind techniques, creating whirlwinds that shredded the serpents, but the effort drained her stamina. 

Ethan observed their movements carefully, his mind analyzing their breathing techniques. Each style was unique, their mastery of themselves was impressive. But to Ethan, they were tools—tools he intended to claim even thought they had unlocked their demon slayer mark these mark's were still unable to stop the rise of the demon king.

As the battle raged, Ethan decided it was time to turn the tide. He activated his Umbra Tendrils Mode a maelstrom of razor-sharp tendrils cleaved and sliced through the slayers forcing them into a defensive position. 

"You're strong," Ethan admitted, his voice carrying a note of mockery. "But your strength is wasted on your futile cause. I can offer you something greater." 

"We don't need your offers, monster!" Shinjiro spat, charging at him with renewed vigor. 

Ethan sidestepped the attack, his hand morphing into a blade that pierced Shinjiro's shoulder. With a surge of biokinetic energy, Ethan injected his blood into the Hashira. 

Shinjiro cried out in agony, his body convulsing as the demon blood began to take effect. 

"What... what are you doing to him?!" Kiyomi shouted, her eyes wide with horror. 

"Preparing my meal" Ethan replied, his tone cold. "You'll see soon enough." 

Shinjiro's transformation was swift. His silver hair darkened, and his once-human eyes turned a deep crimson. His body grew stronger, his aura more menacing. 

"Shinjiro!" Daichi shouted, rushing to his comrade's side. 

But Shinjiro turned on him, his newfound strength overwhelming Daichi's defenses. With a single strike, he disarmed the Crimson Fang Hashira, pinning him to the ground. 

Ethan approached, his gaze fixed on Daichi. "You have fire in you," he said, crouching beside the fallen slayer. "It would be a shame to let it burn out." 

Before Daichi could respond, Ethan plunged his claws into the Hashira's chest, injecting his blood. Daichi's screams echoed through the chamber as his body twisted and transformed. 

Kiyomi stood frozen, her mind racing. She knew she couldn't face Ethan alone, but retreating meant abandoning her comrades. 

"You're next," Ethan said, his crimson eyes locking onto her. 

As Ethan's blood coursed through the slayers' veins, corrupting their bodies and minds. Shinjiro, Daichi, and even Kiyomi succumbed, their human forms replaced by monstrous, demonic versions of themselves. 

"You see?" Ethan said, addressing his newly turned minions. "This is the power I offer. You are no longer bound by the limitations of mortality. You are stronger, faster, and more resilient than ever before." 

Shinjiro knelt before Ethan, his voice trembling with a guttural growl. "What have you done to me, monster? Why can't I control my body?" 

Ethan smirked, his satisfaction evident. "Oh this is my improved blood hex i can finally remotely control my demons but for you guys this is only the beginning of your hell. The only reason you three are still alive is just to test a theory of mine." 

As Ethan approached the now grotesque slayers, an instinctual terror gripped them. Their bodies trembled as though they already knew the horrors about to unfold. 

Ethan's hand began to shift, grotesquely morphing into a monstrous appendage—a giant gaping maw lined with countless, unnaturally scattered teeth. The slayers could only watch in paralyzed dread, their trembling now uncontrollable. 

Without hesitation, Ethan began consuming them one by one. Their screams faded as he absorbed their knowledge, their breathing techniques, and their muscle memory into his own flesh and blood. Yet, despite this gruesome power, the elusive Demon Slayer Mark remained beyond his grasp he needed more experiments. 

But for now, their strength and wisdom coursed through him, reforging him into something far greater—a stronger, more terrifying version of himself. 

From Shinjiro, he gained mastery over Steel Breathing, a technique that emphasized impenetrable defense and overwhelming offense. From Daichi, he claimed the secrets of Flame Breathing, its fiery strikes now merging with his own flesh and blood.

When it was Kiyomi's turn, Ethan paused, studying her trembling form. "You were the strongest of them," he said, his tone almost admiring. "Your wind techniques are truly remarkable." 

Kiyomi glared at him, defiance still burning in her eyes. "You may take my body, but you'll never take my will." 

Ethan smirked. "We'll see." 

As he consumed her, a surge of power coursed through him. The mastery of Wind Breathing became his, its techniques blending seamlessly with his very being. 

As Ethan stood alone in the chamber, his power now magnified by the strength of the fallen Hashira. Kyogan and Azara watched in awe, their loyalty to their king solidified. 

"With their techniques," Ethan said, his voice resonating with dark energy, "I am no longer a mere Demon King. I am the embodiment of perfection." 

Azara bowed deeply. "What are your orders, my lord?" 

Ethan's crimson eyes burned with ambition. "We march on the Demon Slayer Corps. With their strongest warriors now part of me, their defeat is inevitable." 

As the fortress plunged into darkness, Ethan's laughter echoed through the halls, signaling the dawn of a new, terrifying era. The Demon King was no longer content with ruling the night—he intended to claim the world.