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

The sun had barely risen when the Hashira, freshly motivated after the night's feast, gathered in the courtyard once again. The official Advanced Training Arc was about to begin, and spirits were high. Well, for everyone except Saitama.

He sat on the sidelines, legs crossed, looking blankly at the sky.

"Alright, Saitama," Tengen began, his voice dramatic as ever. "Today you'll experience the pinnacle of Demon Slayer training — a program so intense, it's shaped legends!"

Saitama yawned. "Yeah, yeah."

Ignoring the bald hero's lack of enthusiasm, Rengoku stepped forward, flames practically bursting off his cape. "Our first task: The Hell Mountain Sprint!"

He pointed toward a towering mountain in the distance, steep and covered in jagged rocks and thorny vines. The goal? Run to the peak, retrieve a flag, and return in under 20 minutes.

The Hashira all braced themselves mentally. Even for seasoned warriors, this was brutal.

Saitama stood up, hands in pockets. "That's it?"

Before anyone could answer, Saitama casually took a single step — and disappeared. A gust of wind followed, sending leaves spiraling into the air.

The Hashira stared at the now-empty space where Saitama had stood.

Two seconds later, Saitama returned, holding the flag with one hand and a daikon radish he found at the peak with the other.

"Done. Got bored up there, so I picked this," Saitama said, inspecting the radish. "Fresh."

The Hashira fell to the ground in unison.

---

Task Two: Waterfall Endurance

The second challenge was a test of endurance — standing under an icy waterfall for hours to harden both body and spirit. Shinobu explained the benefits of temperature shock to the muscles while Giyu demonstrated his impeccable form.

Saitama stood under the waterfall for exactly ten seconds.

"Too cold," he said, stepping out and grabbing a towel. "And pointless."

"Pointless?!" Sanemi roared. "This is the training that forged our willpower! It separates weaklings from warriors!"

Saitama stared blankly at him. "My bathroom's showerhead is stronger than that waterfall."

The waterfall spirit cried that day.

---

Task Three: Breathing Mastery

The next challenge focused on mastering Total Concentration Breathing. Each slayer had to balance a cup of water on their head while performing breathing exercises, making sure not to spill a single drop.

The Hashira performed with grace, each perfectly controlling their breath.

Saitama placed the cup on his head, stood completely still for ten minutes, then sneezed, sending the cup flying into orbit.

"Oops."

At this point, the Hashira were beyond words.

---

The New Threat

Far away, deep in the shadows of an abandoned temple, the Upper Moons gathered before Muzan. The air was thick with unease.

"This Saitama," Muzan spoke, his voice slow and deliberate, "must not be allowed to disrupt my plans."

Douma, Upper Moon Two, flashed his usual smile. "A bald human who killed a Lower Moon in one punch? Sounds hilarious! I wanna meet him."

Akaza cracked his knuckles, a spark of excitement in his eyes. "If he's that strong, fighting him will finally make my blood boil."

Kokushibo, the ever-serious Upper Moon One, remained silent, but his six eyes gleamed with interest.

Muzan raised his hand. "You will all observe for now. But if Saitama becomes a true threat, eliminate him."

The Upper Moons bowed, though inside, some were already planning their personal confrontations with this mysterious bald slayer.

---

The Hashira's Secret Plan

That night, the Hashira gathered secretly in Tengen's room. Frustration hung heavy in the air.

"This is impossible," Sanemi growled. "How do you train someone who's already… whatever Saitama is?!"

"I think he's just a really strong, bald ghost," Mitsuri whispered.

"He's not a ghost," Giyu said flatly. "He eats too much for a ghost."

"Then what is he?" Shinobu mused. "He's immune to poison, invulnerable to blades, immune to fire, and faster than sound. That's not human."

Rengoku, ever the optimist, smiled brightly. "It doesn't matter what he is! He's our comrade now! We simply need to find training that even Saitama finds challenging!"

The Hashira exchanged uneasy glances.

"That's… impossible," Obanai muttered.

But Mitsuri's eyes sparkled with an idea. "What if we don't train his body — but his heart?"

They all turned to her in confusion.

"We've seen it," she continued. "Saitama is lonely. Detached. He doesn't even seem happy when he wins. Maybe… his real training is learning to care about something again."

The Hashira considered this. It was a strange plan, but it was the only plan.

---

Daybreak

The next morning, Saitama found the Hashira lined up, all wearing friendly smiles that were definitely forced.

"Today's training," Mitsuri announced, "is a special team bonding exercise! We'll cook breakfast together!"

Saitama's face went blank. "...That's training?"

"Of course!" Tengen sparkled. "Cooking teaches cooperation, focus, and love! It's the ultimate Flame Breathing experience!"

Saitama sighed deeply. This was going to be a long day.

---

The Breakfast Disaster

What followed was the most chaotic breakfast session in Demon Slayer history. Rengoku tried to cook eggs by breathing fire directly at them. Shinobu added deadly poison by accident, forgetting humans couldn't eat her 'special seasoning.' Sanemi chopped vegetables so violently the table broke. Obanai's snake stole half the ingredients.

And Saitama?

He made instant ramen.

They all stared as he slurped noisily.

"You call that cooking?!" Sanemi screamed.

"It's fast," Saitama shrugged. "And tastes fine."

Despite the disaster, the Hashira couldn't help but laugh — even Giyu cracked the faintest smile.

And in that moment, for the first time since arriving, Saitama felt something too.

Maybe this whole Demon Slayer thing wasn't so bad after all.

---

End of Chapter 75