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

The battlefield was silent for a moment, except for the howling wind sweeping over the destruction. The Demon Slayers, bruised and exhausted, could only watch in disbelief as Raizen stood back up, his body barely holding together.

Tanjiro's breathing was heavy. "Even after all that… he's still standing?"

Zenitsu clutched his head, on the verge of a breakdown. "I hate this! I HATE THIS! JUST STAY DOWN ALREADY!"

Rengoku, his grip on his sword tightening, watched carefully. "No… something is off. He's not regenerating as quickly anymore."

They all turned their eyes back to Raizen.

---

A Demon on the Brink

Raizen staggered forward, blood dripping from his mangled body. His left arm was completely gone, his ribs exposed, and his right eye was missing. But despite his injuries, his grin never wavered.

"This… this is exhilarating," he wheezed, his voice both strained and excited.

Saitama tilted his head. "Really? You're kinda falling apart."

Raizen chuckled weakly. "That's what makes it fun…"

His body twitched violently, veins bulging, muscles shifting.

A last-ditch transformation.

Tanjiro gasped. "He's forcing his body to evolve again?!"

Rengoku's expression darkened. "If he continues like this, he might become something even worse."

But then—

CRACK!

Raizen's body froze.

The energy surrounding him flickered and collapsed. His remaining eye widened in horror.

"W-What?!"

Cracks spread across his skin like glass breaking. His body was rejecting the transformation. His regeneration had reached its limit.

Tanjiro's eyes widened. "It's happening! His body can't keep up with Saitama's attacks anymore!"

Zenitsu blinked. "Wait… does that mean…"

Muichiro exhaled. "He's dying."

Raizen looked down at himself, his arms trembling. "No… not like this…"

For the first time in hundreds of years—

Raizen felt fear.

---

The Final Blow

Saitama yawned.

"Are we done now?"

Raizen's entire body shook. He knew that one more hit would be the end of him.

But despite the fear creeping in, despite his body falling apart—

He laughed.

"Heh… Heheheh…"

Saitama raised an eyebrow. "What's funny?"

Raizen looked at him, his bloody grin wide. "I've lived for so long… fought countless battles… but you, Saitama… you are the only one who truly made me feel alive."

His body swayed.

And then—

Saitama vanished.

BOOM!

In an instant, he reappeared right in front of Raizen.

A single punch.

A simple, effortless strike.

And Raizen's chest exploded open.

His entire body was obliterated—reduced to nothing but dust, scattering into the wind.

A hush fell over the battlefield.

Saitama looked at his fist. "Huh. Guess that's it."

---

Silence… Then Celebration?

Nobody moved. Nobody spoke.

The reality of what just happened took a while to settle in.

Then, Zenitsu fell to his knees, sobbing. "IT'S FINALLY OVER! I CAN GO HOME!"

Inosuke threw his swords into the air. "I KNEW BALDY WOULD WIN! I NEVER DOUBTED HIM!"

Muichiro exhaled, sheathing his sword. "That was… something else."

Tanjiro watched as the last remnants of Raizen faded away, his heart pounding. "Saitama-san… really did it."

Rengoku nodded. "That was beyond anything we could've handled. Saitama-san… saved us all."

The realization spread.

They had won.

---

But Not Everyone Was Happy

Far away, in the depths of the Demon Realm, Muzan Kibutsuji sat upon his throne.

His crimson eyes narrowed.

"The strongest Upper Moon… destroyed?"

His fingers tapped against the armrest. "Saitama… you are proving to be quite the nuisance."

A shadow moved in the darkness.

A new demon stepped forward. One even more terrifying than Raizen.

"Shall I handle it, Lord Muzan?"

Muzan's lips curled into a sinister smile.

"Yes… let's see how Saitama fares against you."

---

To Be Continued…