The One Punch Man (a.k.a Saitama) in Demon Slayer

The sun was just beginning to set over the mountains, casting an orange glow over the Hashira Training Grounds. The air was thick with tension as Saitama stood in the center, his blank expression unchanged. Around him, the Hashira and demon slayers observed, still struggling to grasp the true extent of his power.

Training Begins

Rengoku stepped forward, his eyes filled with determination. "Saitama-dono! Your strength is unmatched, but true warriors refine their skills! Allow me to train you in Flame Breathing!"

Saitama blinked. "Huh? But I already punch pretty hard."

Ignoring him, Rengoku swung his sword, the flames trailing in the air as he demonstrated precise forms. "Watch closely! The First Form—Unknowing Fire!" He dashed forward with blazing speed, stopping just before Saitama.

Saitama yawned. "Yeah, cool fire sword."

Tanjiro, watching from the side, smiled. "Saitama-san, even if you're strong, refining techniques can make you more efficient!"

Saitama sighed but mimicked the stance halfheartedly. He threw a casual punch in Rengoku's direction—accidentally sending a shockwave that nearly knocked the Flame Hashira off his feet. The ground cracked beneath them.

"AH HAHAHA! SUCH RAW POWER!" Rengoku laughed, brushing off the dust. "LET'S CONTINUE!"

The Hashira continued demonstrating techniques, with Saitama copying them lazily. Despite his lack of effort, his movements were terrifyingly effective, making even the most experienced slayers nervous.

Unexpected Battle

Just as training intensified, a deep, sinister laughter echoed through the trees. The air turned frigid.

From the shadows, a new Upper Moon demon emerged—Upper Moon Four: Juroku. He was a monstrous figure with obsidian-black skin and molten red veins pulsating across his body. His eyes glowed with a malevolent hunger.

"How fortunate," Juroku sneered. "To find all the Hashira gathered in one place… and this bald man. Who might you be?"

Saitama tilted his head. "Oh, me? I'm just a guy who's here."

Juroku smirked. "A foolish one, it seems."

Before anyone could react, the demon lunged at Saitama, his claws aiming for his throat. The Hashira moved instantly, but—

BOOM!

Saitama didn't even flinch. His hand casually caught the demon's wrist, stopping him mid-attack.

Juroku's face twisted in shock. "W-What?!"

Saitama stared at him blankly. "You done?"

With a flick of his wrist, Saitama sent Juroku flying through several trees, his body bouncing like a ragdoll. The demon screeched in agony as he crashed into a boulder, leaving a massive crater.

Silence.

The Hashira stood frozen. Even Muzan's most powerful demons had never been dispatched so effortlessly.

Character Development

Juroku groaned, regenerating instantly, but his confidence was shaken. He had fought countless demon slayers, yet none had neutralized him so easily.

For the first time, a demon of his rank felt fear.

"You… you're not human," Juroku muttered.

Saitama sighed. "Yeah, I get that a lot."

Rengoku, Tanjiro, and the others exchanged glances. Saitama wasn't just strong—he was an entirely different kind of existence.

But even with such power, he remained… indifferent.

Tanjiro, stepping forward, clenched his fist. "Saitama-san… Do you ever struggle? Even if you're this strong… do you have something you're fighting for?"

Saitama blinked, caught off guard by the question.

A brief silence.

Then, he scratched his head. "Hmm… I guess I'm still figuring that out."

Juroku, now enraged, prepared for a second attack—but Rengoku stepped forward, sword blazing. "Enough talk. If you stand in the way of humanity, we shall cut you down!"

The battle was about to continue.

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End of Chapter 78