Ryuya had long understood one thing—
If Muzan ever decided to kill him, he would not wait quietly for death.
Breaking free from Muzan's control was not merely ambition.
It was survival.
As for peace between humans and demons… that had never been his concern before meeting Kanae.
Good and evil were standards defined by humans, not by heaven.
But for Kanae—
He was willing to reshape the future.
Not for morality.
Not for justice.
Simply because he loved her.
That alone was enough.
"I understand," Kanae said softly, holding his arm with quiet trust.
Kotetsu soon stopped before a clearing in the forest.
There stood Yoriichi Type Zero.
A mechanical doll modeled after Tsugikuni Yoriichi.
Six arms extended from its body, each capable of wielding a Nichirin Blade. Its face, earrings, hair, and clothing closely resembled the legendary swordsman.
Ryuya studied it carefully.
Master really does resemble his younger brother.
The resemblance between Kokushibo and Yoriichi was undeniable.
The thought amused him.
If Kokushibo disguised himself as Yoriichi and appeared before Muzan…
Muzan might split into pieces on the spot.
"Y-you've seen it now," Kotetsu stammered. "Please don't hurt the villagers. And let me go."
Ryuya crouched down slightly.
"I keep my promises. But I never said I'd release you immediately."
Kotetsu's face went pale.
"That's going back on your word!"
"No," Ryuya replied calmly. "I said I'd let you go. I didn't say when."
Kanae stepped forward gently. "Don't worry. We won't harm you."
Kotetsu hesitated, then chose to take Kanae's hand rather than Ryuya's to stand.
Ryuya snorted lightly but said nothing.
With a smooth motion, he drew his Nichirin Blade.
Without warning—
He attacked.
"Moon Breathing, Second Form: Flowing Moon!"
Two massive crimson crescent blades tore through the air.
Golden fragmented crescents spiraled along their edges, scattering into countless smaller slashes.
Click.
Yoriichi Type Zero activated.
Its internal mechanisms shifted.
Six arms moved stiffly yet swiftly, each blade cutting outward in synchronized arcs.
"Sun Breathing, First Form: Dance."
Ryuya immediately recognized the technique.
Though the doll lacked true breathing, it replicated the sword forms of Sun Breathing with mechanical precision.
"Sun Breathing, Second Form: Clear Blue Sky."
"Sun Breathing, Third Form: Raging Sun."
The doll cycled through forms methodically.
Its flaw was obvious.
It could not adapt.
It executed commands in sequence, regardless of the opponent's movement.
Though it deflected the primary crescent blades, the countless smaller moon fragments sliced through its wooden body.
Crack.
Two arms were severed instantly.
Blades clattered to the ground.
"Too rigid," Ryuya murmured.
The doll's movements were precise—but predictable.
Unlike a living swordsman, it lacked instinct.
Unlike Kokushibo… or Yoriichi.
Ryuya pressed forward.
"Moon Breathing, Third Form: Loathsome Moon, Chains."
"Moon Breathing, Fourth Form: Heavenly Flower Invites the Moon."
Crescents layered upon crescents.
The remaining arms of the doll struggled to respond.
Wood splintered.
Gears cracked.
Fragments scattered across the forest floor.
Kotetsu gasped in horror.
But Ryuya's eyes were sharp—not focused on destruction, but on observation.
Even in its limitations, the doll carried traces of Sun Breathing's structure.
Its transitions.
Its flow.
He had only practiced Sun Breathing superficially using Makomo's blade.
But watching the doll confirmed something important.
Sun Breathing's foundation differed fundamentally from Moon Breathing.
Where Moon Breathing fragmented and multiplied pressure—
Sun Breathing unified.
Direct. Radiant. Relentless.
Interesting.
Then another thought surfaced.
Tokito Muichiro.
Descendant of the Tsugikuni bloodline.
A prodigy who became the Mist Hashira within two months.
Master would be interested.
Very interested.
Perhaps the Demon Slayer Corps would soon place their hopes on that child.
And perhaps—
Ryuya might take him first.
A faint smile appeared on his face.
The mechanical doll attempted one final motion.
Ryuya stepped forward calmly.
One clean slash.
The torso split.
The head rolled aside.
Yoriichi Type Zero collapsed completely.
Silence filled the forest.
Ryuya walked toward the broken body and examined the interior.
Hidden within—
A Nichirin Blade.
Old.
Yet preserved.
The blade once wielded by the real Yoriichi.
Ryuya grasped the hilt slowly.
A faint warmth lingered in the metal.
He lifted it.
Sunlight did not shine here—
Yet the blade seemed to carry its memory.
Behind him, distant tremors echoed.
The Hashira had likely arrived at the village.
Time was nearly up.
Ryuya sheathed the ancient blade carefully.
"Let's go," he said to Kanae.
The true battle was about to begin.
...
Author's Note:
The full completed version of Demon Slayer: Son of Muzan (Completed) is now on Patreon!
🔥 I also have additional 18+ fanfics available for readers who enjoy exclusive mature stories. 😉
1. Dragon Ball: Oolong's Sex Adventure
2. Elements of Lust – ATLA & Korra Mixed Smut
3. Doraemon: Filtering with Nobi Tamako
4. The Naive Me Who Became Someone's Everyday Secret
5. High School DxD: Rias Gremory, the Phenex Bride
6. Versatile Mage: Awakening the Succubus System
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