Chapter 15: Muzan’s Headache – When Legends Clash
In the depths of an ancient castle, where the walls pulsed like living flesh, Muzan Kibutsuji sat on his throne. His crimson eyes glowed faintly as a trembling Nakime played her biwa, shifting the endless corridors around them.
A chilling silence filled the room — the kind that came before a storm.
Before him knelt Douma, covered in frost and fear sweat, while Akaza was absent — because Akaza was still unconscious, halfway buried inside a mountain.
"This is what you're telling me…" Muzan's voice was calm, but the air itself grew heavy, like the castle was suffocating under his rage. "A bald human — not a demon, not a slayer — effortlessly defeated Upper Moon Three… and humiliated Upper Moon Two?"
Douma forced a smile, but his trembling hands betrayed him. "Ahaha! It sounds ridiculous, doesn't it, Muzan-sama? But I saw it with my own eyes! This guy didn't even use a sword, breathing, or anything! He just stood there and flicked Akaza into orbit!"
Muzan's eyes narrowed.
"How could such a man exist… without me knowing?"
The fact that such anomaly existed outside of his control made Muzan's very blood boil.
"Describe him."
"He's… bald."
"...Bald?"
"Yes! Shiny like the moon! And his expression—" Douma gulped. "He looks… bored. Not angry, not bloodthirsty, just… like none of us are even worth his time."
That struck a nerve.
Muzan, the progenitor of all demons, the being who had lived for over a thousand years, had never been dismissed like that.
He stood up, his aura pouring out like liquid darkness. "Gather all the remaining Upper Moons. I will deal with this 'Saitama' personally."
---
Back at the Butterfly Estate
It was early morning, and Saitama was sprawled on the roof, snoring peacefully. The Hashira, however, were in full panic mode.
"We need to form strategies! We need a new training regimen! We—" Tomioka stopped mid-sentence as Saitama rolled over, almost falling off the roof.
"Why are you panicking?" Saitama yawned, sitting up. "I punched that ice guy and the angry martial arts dude. Problem solved, right?"
Shinobu's eyebrow twitched. "That's not how it works! Muzan will definitely retaliate. He won't sit still after hearing what you did."
"Muzan? Who's that?"
The room went silent.
"Saitama-san," Tanjiro said carefully, "Muzan is the Demon King, the source of all demons. The most dangerous enemy we have."
"Oh." Saitama scratched his cheek. "Okay. Where is he? I'll punch him."
"...Just like that?"
"Yeah." Saitama blinked. "Isn't that what you do with bad guys?"
---
Demon Slayer HQ Meeting
All the Hashira gathered for an emergency meeting — even Sanemi, who usually hated group talks.
"We can't just rely on Saitama-san for everything," Gyomei said, prayer beads clicking in his massive hands. "He may be strong, but we have our own duty as slayers."
"But still," Tengen said, stroking his chin. "Having someone like him is… pretty flashy. Imagine the headlines: 'Bald Man Ends Thousand-Year Demon Reign in One Punch!'"
"Focus!" Iguro hissed. "We need to figure out how to assist him, not just watch."
"Maybe we should just let him handle it," Zenitsu whispered. "He's basically a walking catastrophe."
Before they could argue further, the sky darkened unnaturally, and a chilling presence filled the air.
---
Muzan Arrives
A red moon rose in broad daylight. The air itself vibrated as Muzan descended, standing in the clearing right outside the estate. His pale skin glowed faintly, and his eyes burned with ancient malice.
The Hashira instantly went on guard — swords drawn, breathing techniques activated.
Muzan, however, wasn't looking at them.
His gaze was locked solely on Saitama, who was sitting on the porch, casually picking his ear.
"So you're the one." Muzan's voice was low, dangerous. "The bald man who humiliated my demons."
Saitama looked up. "Oh. You must be Muzan. Finally."
Muzan expected fear, awe, maybe a battle stance.
Instead, Saitama stood up, stretched, and cracked his neck. "Let's get this over with. I need to get back before dinner."
---
Muzan vs. Saitama – First Contact
Muzan vanished — appearing directly in front of Saitama, fingers stretched into claws aimed for his heart.
Saitama didn't move.
Ding!
Muzan's claws hit Saitama's chest… and broke instantly, like glass hitting steel.
"...Huh?"
Before Muzan could process, Saitama lightly flicked his forehead.
Muzan was sent flying through several trees, bouncing like a skipping stone across a lake.
The Hashira stood in shocked silence.
"Did… did he just do the same thing to Muzan as he did to Akaza?" Mitsuri gasped.
"Yup," Saitama said. "All these demons are way too fragile."
---
Muzan's True Form Awakens
From the debris, a new figure emerged. Muzan's body twisted and mutated — growing twelve massive tentacles, mouths lined with fangs opening along his arms and back. His skin turned darker, his veins glowing like molten lava.
"This is my true form, Bald Man!" Muzan roared. "Tremble before my—"
"Okay," Saitama cracked his knuckles. "Serious Series: Serious Punch."
He threw a casual punch in Muzan's direction.
BOOOOOOM!
The entire forest behind Muzan vanished. Trees, mountains, rivers — all disintegrated into mist. Muzan himself was blown apart into countless tiny chunks.
The Hashira's jaws dropped.
"Is… is he dead?" Kanao whispered.
"No," Saitama sighed. "These boss-type guys always regenerate."
And sure enough — the chunks of Muzan's flesh began writhing, crawling back together. But the process was painfully slow, like Muzan's very cells were terrified of reforming.
Saitama tapped his foot, waiting.
"This is annoying," he muttered. "How do you kill demons permanently?"
"Sunlight," Tanjiro said quickly.
"Okay." Saitama grabbed Muzan's half-reformed head and threw him straight up — so high, he pierced the stratosphere, heading directly for the rising sun.
The Hashira could only watch in awe.
"Well," Saitama dusted his hands. "That should do it."
"Just… like that?" Rengoku's spirit (because let's face it, he's probably watching from heaven) screamed proudly. "Amazing!"
---
Peaceful Morning
The sun rose fully, and for the first time in centuries, the air felt lighter. The curse of Muzan… was over.
"So, what now?" Saitama asked.
"You… you ended the war," Tanjiro said, tears in his eyes. "You saved everyone."
"Cool. What's for breakfast?"
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End of Chapter 15