Deep within the corridors of the Infinity Castle, the air was thick with black mist that curled along the floor, filling the space with a suffocating stillness.
The moment Giyu stepped into the passage, hurried footsteps echoed behind him. Akaza burst out of the darkness, his body still crackling with lingering fighting aura. His short pink hair clung to his face, and his golden eyes burned with fury.
He grabbed Giyu's wrist roughly.
"Mushiki! Why did you order a retreat?! We could have wiped them out—every single one of those Hashira! Why did you run? What the hell are you thinking?!"
Giyu's wrist throbbed with pain under Akaza's iron grip, but his face remained unreadable. He calmly pulled free and spoke in a low, steady voice, his tone utterly flat.
"The situation wasn't right. The Demon Slayer Corps sent four Hashira at once. That means it was a setup. If we kept fighting, we'd be trapped and delay Lord Muzan's plan."
"Not right? Don't make me laugh! You were scared to fight, that's what!"
Akaza roared, stepping forward, his fists trembling, black aura swirling tightly around his knuckles.
"When you fought those two Hashira, you were holding back—I saw it! Don't tell me you still feel sympathy for them. Do you still see those humans as your comrades?!"
Giyu didn't answer. He turned slightly, stepping away toward his quarters. Arguing with Akaza was pointless. Every word risked exposing the truth he'd fought so hard to conceal.
But after only a few steps, a cold, crushing pressure flooded the corridor behind him.
He froze instantly.
That aura—icy, suffocating, and absolute—belonged to only one being.
Muzan.
Akaza's fury vanished in an instant, replaced by paralyzing fear. His entire body stiffened as he turned toward the corridor's shadows and dropped to one knee.
"Lord Muzan..."
Giyu's chest tightened. He turned as well, and from the darkness emerged a pale pink figure.
Muzan Kibutsuji.
The dim light caught the gleam of his crimson eyes—cold, merciless, fixed directly on Giyu.
"Mushiki," Muzan's voice dripped with venom, each word slicing through the air like a blade, "your recent behavior has disappointed me."
Without warning, Muzan extended his right hand. His fingers sharpened into black talons, which shot forward like a striking serpent, stabbing straight into Giyu's temple.
A searing pain exploded through his skull. Giyu tried to resist, but his body was instantly locked in place by Muzan's invisible power. He couldn't move—not even a finger.
He could feel the energy flooding his mind, the black tendrils of Muzan's will invading his consciousness, scraping against a deep, hidden scar within him.
That mark—
It was the seal Muzan had left inside his brain long ago during his first inspection.
Now, as Muzan's power surged into it, the mark began to spin and churn like a grinding wheel, tearing through his thoughts.
His memories began to collapse.
Shinobu's gentle smile.
Tanjiro's determined eyes as he raised his Nichirin sword.
Oyakata-sama's warm voice saying, "I trust you."
Tomioka To's eager expression when he first mastered using two Breathing Styles…
Each image shattered like glass, scattering into nothing before being consumed by darkness.
"No… no… please don't…"
A broken whisper slipped from Giyu's throat. Tears streamed down his face uncontrollably as he struggled to grasp at vanishing fragments—shadows of the people he loved, the memories that defined him.
He wanted to remember who he was. He wanted to remember their faces, their warmth—anything. But the harder he reached, the faster everything slipped away.
"You don't need human emotions," Muzan said coldly, his voice echoing in Giyu's mind like an endless winter storm. "You don't need those useless memories. They only weaken you."
His hand pressed deeper into Giyu's temple.
"Remember this instead: you are Upper Moon Two, my sharpest weapon. Your purpose is to annihilate the Demon Slayer Corps and find the Blue Spider Lily for me."
As those words sank into his mind, the emptiness inside Giyu began to fill again—
but not with truth.
With false memories.
In those new memories, he was no longer Tomioka Giyu.
He was Mushiki, born from Muzan's blood, created only to serve.
He was born as Upper Moon Two, wielding a powerful Blood Demon Art rooted in water and mastery over multiple Breathing Techniques. His one and only purpose—serve Muzan, and kill every human who dares defy him.
The memories of Tomioka Giyu—the bonds with the Demon Slayer Corps, the warmth of those who once fought beside him—were gone. Every trace of his past had vanished completely, as if it had never existed.
Muzan withdrew his claws. A small wound remained at Giyu's temple, but it healed almost instantly.
He staggered back two steps, his once-clear eyes now empty and cold. The faint gentleness and conflict that had once lingered there had completely disappeared, leaving behind only the merciless instincts of a demon and absolute obedience to Muzan.
He dropped to one knee, his voice devoid of emotion.
"Subordinate Mushiki, reporting to Lord Muzan."
"Excellent."
A faint, satisfied smile appeared on Muzan's face. His crimson eyes shifted toward Akaza.
"Akaza, from now on, you'll work with Mushiki. You two will lead the purging of Demon Slayer bases. Remember this—Mushiki's orders are the same as my own."
"Yes, Lord Muzan!"
Akaza bowed deeply, but when he lifted his gaze toward Mushiki, there was something new in his eyes—wariness.
The aura radiating from Mushiki now was far colder, sharper, and far more dangerous than before. There was no trace of hesitation, no lingering humanity.
He was, in every sense, a true Upper Moon.
A second coming of Kokushibo himself.
Without another word, Muzan's form dissolved into the darkness of the corridor and vanished.
Giyu—no, Mushiki—slowly rose to his feet. His dark-blue slit pupils flickered faintly as he glanced at Akaza.
He meant to say only one thing: from now on, he expected full strength from his comrade in battle.
"Show your real power, Akaza."
His tone was calm and detached, his expression lifeless. Then he turned and walked toward his room, each step steady, his back perfectly straight—no trace of hesitation or emotion left.
Akaza's jaw tightened, his fists trembling as veins bulged on his forehead.
"Are you looking down on me, Mushiki…?"
He glared at the retreating figure, teeth grinding, before vanishing from sight in frustration.
...
Meanwhile, inside the laboratory of the Butterfly Mansion, Kocho Shinobu held a glass dropper carefully over a test tube. She slowly released a few drops of pale-green liquid into it.
Tiny bubbles began to rise within—the final stage of her newly improved "Cellular Hallucination Agent."
It was nearly complete.
But suddenly, her heart lurched violently, as though seized by an invisible hand. Pain radiated through her chest, forcing her to stop mid-motion. The dropper nearly slipped from her trembling fingers.
A chill ran up her spine, spreading through her entire body. Her breath caught as she shuddered uncontrollably.
"What… what is this?"
Shinobu clutched her chest, gasping, her face turning pale.
She didn't know where the fear came from, but her thoughts instantly turned to one person—Giyu.
Ever since they had parted ways in the Entertainment District, she had been working tirelessly, formulating medicines each day while waiting for a signal from him.
But these past few days, she hadn't received anything—no coded message, no update.
She had already felt uneasy. Now, that sudden surge of panic made her heart ache even more.
She walked to the window. Outside, wisteria flowers were in full bloom, their petals swaying gently in the night air.
The sight that usually brought her peace only deepened the emptiness inside her.
An indescribable sense of loss pressed on her chest, a haunting feeling that something precious had slipped away forever.
"Tomioka-san…"
Her soft whisper trembled, laced with a sorrow she couldn't fully name.
"What happened to you? Did something… go wrong?"
She reached into her pocket and touched a small vial of the same green solution—the improved "Cellular Hallucination Agent."
It was meant for Giyu. She'd planned to give it to him the next time they met.
But now, the thought of that next meeting filled her with fear.
In the lab, the test tubes continued to bubble quietly, and outside, the wisteria flowers still bloomed in serene beauty.
Yet Shinobu's heart had sunk completely into darkness.