The forest had gone silent. No crickets, no wind, not even the rustle of leaves. Every living thing had fled.
Upper Moon One stood fifty yards ahead, perfectly still. The moonlight illuminated his figure—tall, imposing, draped in a purple nagagi kimono adorned with an intricate flower pattern. His red hakama pants completed the traditional ensemble. At his waist hung a flesh-like katana, its surface grotesque and organic, pulsing as though alive.
But it was his face that stole the breath from our lungs.
Six eyes. Three pairs arranged vertically across his face—each one golden-yellow with red sclera, the kanji for "Upper Moon" and "One" etched into the middle and lower pairs respectively. Flame-like markings spread across his forehead and down his chin in dark red. His shoulder-length hair, black streaked with dark red, spiked wildly around his face.
His expression was empty. No rage, no bloodlust, no emotion whatsoever. Just the flat, mechanical observation of a warrior who'd killed for over four centuries.
"U-Upper Moon... One," Tanjiro's voice cracked. "But why? How..."
"L-Lady Tamayo... What should we do?" Yushiro forced the words out, but Tamayo couldn't answer. Her face had drained of color, eyes wide with recognition and terror.
Nezuko pressed against her brother, unable to speak.
The sheer presence radiating from Upper Moon One was crushing. Not killing intent—just existence. The weight of power so vast that resistance seemed laughable.
I extended my senses carefully. Tamayo and Yushiro behind me. Tanjiro and Nezuko, hearts hammering. And ahead—only Kokushibo. No ambush. No backup.
He'd come alone.
I stepped forward.
"Akira-san!" Tanjiro grabbed my sleeve. "Don't! You'll die if you fight him!"
Another step.
"Akira-san, please!" Tamayo's voice shook. "I'll distract him. All of you—run. Now."
"Lady Tamayo, no!" Yushiro seized her arm.
She pulled free gently, her expression soft with sorrow. "I'm sorry, Yushiro. But Akira-san is our hope against Muzan. If he dies here..." She lifted her arm, claws extending to tear into her own flesh. "I'll hold Upper Moon One as long as I can—"
I caught her wrist.
"There's no need for that."
I released her hand and reached into my pocket. The Divine Sword materialized in my grip—a crimson blade that hummed with power. The moment it appeared, every demon present reacted. Tamayo gasped. Yushiro stumbled backward. Even Kokushibo's expressionless face shifted, all six eyes locking onto the weapon.
I settled into my stance—weight balanced, sword held low at my right side, ready to draw or strike in an instant. Hiten Mitsurugi-ryū's fundamental position.
"I've been traveling this world hunting demons," I said. "I'm lucky to stumble across Upper Moon One."
My voice dropped, losing all humor. "Don't interfere. Don't try to help. If you interrupt this fight, his blade will kill you before you blink." I glanced at Tamayo. "Trust me."
Silence. Then, barely audible: "Understood."
Kokushibo's lips moved. His voice emerged deep and measured, each word carrying centuries of weight.
"You... are not human... are you?"
I felt my eyebrows rise.
He could see it. Through those six eyes—the Transparent World, I realized. He was looking through my skin, past muscle and bone, seeing the alien structure beneath. The Viltrumite physiology that made me fundamentally different.
"Is that why you're here?"
"I have orders from my lord." Kokushibo's hand rested on his sword hilt—the gesture casual but laden with threat. "You are to be brought before him. Alive. Along with the medicine you possess."
His six eyes remained fixed on me.
"Surrender. I will grant your companions less painful deaths."
"I refuse."
I shifted my weight slightly, adjusting my stance. The battōjutsu position refined, ready to explode into motion.
Kokushibo's eyes narrowed—all six of them studying my form with intense focus. "That stance... I have never encountered it before."
Then I moved.
The world blurred. Trees became streaks of shadow. Distance collapsed into nothing. My blade sang through the air, aimed directly at Kokushibo's neck—
CLANG!
His sword met mine, the parry perfectly timed despite my speed. The impact sent shockwaves through the forest floor, leaves exploding upward in a spiral.
"Too fast," Kokushibo said, his voice still calm despite the surprise in his eyes. "I underestimated you."
I landed in a crouch fifteen feet away, already resetting my stance. "I underestimated you too. Otherwise your head would've separated from your shoulders just now."
"Did you see him move?!" Yushiro's voice cracked with disbelief.
"No," Tanjiro whispered, his eyes wide. "He just... vanished."
Tamayo stared at the space where our blades had clashed. Her eyes unfocused slightly, seeing something beyond the present moment. An image superimposed over mine—someone from her distant past, a swordsman who'd moved with similar impossible speed..
She blinked, returning to the present, and turned to the others. Her voice was steady now, filled with quiet certainty. "He will kill this demon. Put your trust in Akira-san."
Kokushibo's six eyes tracked my every micro-movement. Then he shifted his weight, his stance changing. "Moon Breathing, First Form."
He launched backward in a blur of motion, his blade cutting through the air in a wide arc. Crescent-shaped slashes materialized from nothing—chaotic, multi-directional attacks that carved through trees and earth with equal ease.
I twisted between them, my body responding on pure instinct. The Hiten Mitsurugi-ryū emphasized reading the opponent's breathing, their killing intent, the subtle shifts in muscle tension that preceded every strike. Against a demon of Kokushibo's caliber, those micro-predictions were the only thing keeping me alive.
"Ryūtsuisen!"
I descended from above like a falling dragon, blade aimed at his skull. Kokushibo pivoted smoothly, his sword rising to intercept. Steel screamed against flesh-blade, sparks erupting in a shower of light.
We separated, circled, clashed again.
"Moon Breathing, Fifth Form: Moon Spirit Calamitous Eddy."
A vortex of slashes erupted around him—countless crescent moon blades spiraling outward in a defensive maelstrom. I ducked, weaved, my blade deflecting the ones I couldn't dodge. Each impact sent vibrations up my arm, but I kept moving, kept pressing.
"Ryūsōsen!"
My blade became a blur—a continuous barrage of strikes from impossible angles, each one designed to overwhelm defenses through sheer speed and unpredictability. Kokushibo's sword moved to meet each one, parrying with surgical precision despite the velocity.
"Your technique..." Kokushibo's voice remained steady even as we exchanged blows faster than the eye could follow. "It prioritizes speed and precision over raw power. Each strike targets vital points. Efficient."
"Your Moon Breathing creates openings through area denial," I countered, deflecting another crescent slash. "You control space, force opponents into predictable patterns."
CRASH!
A tree the width of three men exploded behind me, bisected by a missed slash. Wood splinters filled the air like shrapnel.
"They're too fast," Tanjiro breathed, his Demon Slayer Mark eyes straining to track our movements. "I can only see blurs and hear the swords..."
"The trees," Nezuko whispered, watching another ancient pine collapse. "They're destroying everything around them."
Yushiro's hands clenched. "Lady Tamayo, is Akira really—"
"Watch," Tamayo said softly, her eyes never leaving the battle. "Just watch."
My mind raced even as my body moved on autopilot. Kokushibo would be a perfect addition to my shadow army—centuries of combat experience, devastating techniques, raw power that exceeded most demons. But the moment I killed him, he'd crumble to ash. No body to extract. No shadow to claim.
A waste, but unavoidable.
I parried another combination—three slashes that came from angles that should have been physically impossible. My blade sang, redirecting each strike by millimeters, conserving energy while keeping him from landing a clean hit.
"Doryūsen!"
I dropped low, blade sweeping in a devastating arc aimed at his legs. Kokushibo leaped backward, and I immediately followed up with "Ryūkansen!" My blade whistled horizontally, the air itself screaming as I added rotational force to amplify the cutting power.
His sword came up to block, but the impact forced him back three steps—the first time he'd given ground.
All six eyes widened fractionally.
"Your physical strength... surpasses human limits significantly." Kokushibo's grip adjusted on his sword. "And that blade. What is it made of?"
"Wouldn't you like to know?"
We clashed again, a rapid exchange of twenty strikes in three seconds. Each impact lit up the darkness with sparks. My arms burned with exertion, but I couldn't show weakness. Couldn't give him an opening.
"Moon Breathing, Seventh Form: Mirror of Misfortune, Moonlit."
His technique changed. The slashes came faster now, each one replicating and multiplying mid-flight. What started as five attacks became ten, then twenty, filling the air with a web of crescent blades.
I flowed between them like water, my body remembering patterns drilled through countless hours of practice. The Hiten Mitsurugi-ryū wasn't just about attacking—it was about reading the battle, predicting trajectories, finding the gaps in seemingly impenetrable defenses.
There.
I slipped through a half-inch opening between two slashes, closing the distance in a heartbeat. "Doryūsen!" The upward strike came from his blind spot—except he didn't have blind spots. Six eyes saw everything.
His sword intercepted mine with millimeter precision. We locked, faces inches apart.
"Your swordsmanship..." Kokushibo's voice was soft, almost contemplative. "It reminds me of someone. The efficiency. The lethality. But the style is completely foreign."
"I'll take that as a compliment."
I disengaged with a backflip, landing in a crouch twenty feet away. My breathing was elevated but controlled. Sweat dripped down my temple.
Kokushibo straightened, his six eyes studying me with what might have been respect. Then he raised his sword.
The blade began to change.
The flesh-like katana writhed, organic tissue pulsing and expanding. Additional blade fragments emerged from the main body—smaller curved edges that branched off like crescent moons made solid. The weapon transformed into something that defied conventional sword design, a grotesque fusion of multiple blades that could attack from countless angles simultaneously.
"Your sword style..." Kokushibo's voice carried a note of something that might have been anticipation. "It is formidable. You have earned my acknowledgment"
His stance shifted, weight redistributing with predatory grace.
"Prepare yourself. From this point forward... I will not hold back."
The sword in his hand seemed to hum with malevolent energy, each auxiliary blade catching the moonlight like teeth in a predator's maw.
I tightened my grip on the Divine Sword, feeling its warmth pulse against my palm.
This was about to get interesting.
. . .
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