Infinity Castle.
Magnificent. Brilliantly illuminated. Wooden structures floated in chaotic disarray, arranged without pattern—yet somehow forming a twisted, eerie beauty.
Thump. Thump. Thump.
The steady sound of biwa strings echoed through the vast space as Ryuya walked forward.
He knew the music was guiding him.
Nakime had already teleported Song Yue elsewhere in advance, following prior instructions. She had not been brought here alongside him.
Which meant—
Nakime had summoned him independently.
And that could only happen under the command of two individuals.
Kokushibo.
Or—
Kibutsuji Muzan.
Why the urgency?
Why now?
Lost in thought, Ryuya eventually looked up.
Two folding screens stood before him. Behind one sat Nakime, plucking her biwa calmly.
"Young Master Ryuya."
With a gentle strum, the floor beneath him rose upward.
As he ascended, another figure entered his sight.
Black suit.
Long black hair.
Magenta eyes.
Muzan.
Kibutsuji Muzan's lips curved faintly when he saw his son. Then he cast a playful glance at the woman standing beside him.
Kochou Kanae.
Ryuya's pupils shrank.
Why was she here?
Why was she standing beside Muzan?
A hundred questions flooded his mind at once. Unease crept into his chest.
Seeing Kanae brought a flicker of joy—
But not here.
Not like this.
"Ryuya, you took quite a while to arrive. A bit slow, don't you think? You've wasted time."
"Ryuya…?"
Kanae widened her eyes in apparent shock. She looked between Muzan and Ryuya, confusion written across her face.
"W-What's going on?"
Muzan chuckled softly.
"My apologies, Miss Kochou Kanae. I told you a small lie. In truth, I am not Ryuya."
Her expression shifted to hurt disbelief.
"You… you were lying to me this whole time? Then who are you? Why do you look exactly like him?"
"Lying?" Muzan smiled faintly. "I was merely evaluating my son's future wife. As for our resemblance—perhaps you've mistaken the direction. It is not that I resemble Ryuya. It is that Ryuya resembles me."
A father must always remain above the son.
Status mattered.
"Daughter-in-law…?"
Kanae blinked as if still processing the word.
"As for who I am…" Muzan stepped closer to Ryuya and rested a hand on his shoulder. "Ryuya, why don't you tell her?"
He seemed particularly pleased with Ryuya's stunned expression.
As though he had caught his son red-handed.
Ryuya kept his voice steady.
"He is my father. Kibutsuji Muzan."
From their exchange, he pieced together the situation.
Muzan had impersonated him.
He had spoken with Kanae.
How long? About what?
That was unclear.
But Kanae had clearly believed it was him.
What had Muzan extracted?
Ryuya's thoughts raced.
The Butterfly Mansion.
His dealings near the Demon Slayer Corps.
Those were dangerous—but manageable.
The real danger…
Was Tamayo.
If Muzan had learned about Tamayo—
If Kanae had revealed that meeting—
He would be finished.
Not even Kokushibo could shield him from that.
Then why was Kanae still alive?
Why summon him here instead of simply killing him?
Leverage?
A trap?
Calm down.
Stay calm.
Cold sweat slid down his back.
"Kibutsuji Muzan…? You're the Demon King?"
Kanae murmured, her voice trembling just slightly.
"So Ryuya is actually Kibutsuji Muzan's son? Why has he never mentioned that?"
Ryuya's eyes flickered.
Ah.
Clever.
With a single sentence, Kanae had revealed everything he needed to know.
She had known all along that Muzan was his father.
And she had learned it—
At Tamayo's clinic.
A double meaning.
She was subtly telling Ryuya:
I didn't reveal Tamayo.
Muzan doesn't know.
Ryuya exhaled slowly.
If the circumstances were different, he might have laughed.
Or even pulled her into his arms.
Brilliant.
Truly brilliant.
She had outmaneuvered Muzan without him even realizing.
Now—
It was his turn.
"Ryuya," Muzan said lightly, leaning close. "When did you find such a refined and understanding wife? Why is your father unaware?"
His voice dropped to a whisper near Ryuya's ear.
"How many more things are you hiding from me? Tell me now, and I may choose not to pursue the matter."
His tone was warm.
Almost gentle.
"Son, your father hopes you are an honest child. Seeing Miss Kochou Kanae here, surely you understand certain things now… don't you?"
The threat was subtle.
But unmistakable.
...
Author's Note:
The full completed version of Demon Slayer: Son of Muzan (Completed) is now on Patreon!
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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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