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

This chapter is going to be a long one

The morning sun painted the sky in soft hues of gold and crimson, spilling its light across the sprawling training grounds deep within the Demon Slayer Corps' headquarters. The Hashira stood gathered, each one exuding their own intimidating aura — pillars of strength, resolve, and unshakable will. Yet, despite their usual air of pride and authority, today's atmosphere felt… awkward.

The reason?

Saitama stood at the edge of the field, hands lazily tucked into the pockets of his worn-out hero costume, his expression a blend of mild confusion and faint disinterest. His shiny, smooth head gleamed in the sunlight, almost acting like a second sun. The Hashira couldn't help but stare.

Tengen Uzui was the first to break the silence, flipping his twin blades casually onto his shoulder. "So, this is the so-called 'bald legend'? Doesn't look very flashy to me."

"I dunno," Zenitsu muttered from behind, already trembling. "Something about him makes my stomach feel weird… like I'm staring at a natural disaster in human form."

Giyu Tomioka stood quietly, his usual detached expression in place, but even he found it difficult to completely ignore the strange aura — or rather, lack of aura — surrounding Saitama. It was like staring into a void, and that absence of anything made him more unsettling than even Muzan.

Shinobu Kocho, ever the curious one, stepped forward with her sweet smile. "Welcome to the Demon Slayer Corps' training grounds, Saitama-san. Today, we'll be assessing your… um… combat potential."

Saitama blinked slowly. "Didn't we already do this a bunch of times?"

Rengoku, eyes blazing with his usual fiery spirit, laughed heartily. "True strength can only be revealed through repeated trial by fire! It is the way of the Flame Hashira!"

Saitama scratched his cheek. "I mean, okay. But is this really necessary? I'm not even officially part of your group."

Mitsuri Kanroji clapped her hands excitedly. "But we want you to be! You're so strong, and you saved us, and… well, we'd feel safer if you were fighting alongside us."

Tokito Muichiro, half-listening while staring at a passing cloud, added absently, "It's faster if we just train with him."

That seemed to settle it.

Operation Bald Hero Training Arc was officially underway.

---

First Phase: Swordsmanship Test

Tengen stepped forward, spinning his blades with a dramatic flair. "I'll test his reflexes! After all, what's a Demon Slayer without his sword skills?"

He lunged forward in a flash of muscle and motion, his blades cutting the air faster than most eyes could follow. Even the other Hashira prepared to step in — just in case Saitama couldn't handle it.

But he didn't even move.

The blades stopped centimeters from his skin — as if repelled by some invisible wall of sheer indifference. Tengen's arms trembled, his grip strained. "W-what the hell?"

"Oh," Saitama said, tilting his head slightly. "Are we starting?"

A single flick of Saitama's finger sent Tengen flying across the field, landing in a pile of dirt with a loud, glittery crash.

"Next?" Saitama asked, bored.

---

Second Phase: Breathing Arts Endurance

Rengoku stepped up next, flames erupting around him. "Let's see how you handle the full intensity of Flame Breathing! Prepare yourself!"

He unleashed a blazing barrage of slashes, heat distorting the air itself — the sheer power melting the ground beneath their feet. The other Demon Slayers shielded their eyes.

Saitama yawned.

He casually reached out, catching Rengoku's flaming blade between two fingers. The flames sputtered out like a candle in a storm. "This is kinda warm," he said. "Feels like holding a cup of tea."

Rengoku stood frozen, disbelief battling respect in his expression. "INCREDIBLE!"

---

Third Phase: Speed Trial

Shinobu volunteered to test speed. After all, her Insect Breathing relied entirely on agility and precision. She darted forward with blinding swiftness, her small blade aimed at pressure points.

Saitama walked forward.

Not dodged. Not countered. Just walked — completely ignoring her attacks. Every time her blade should have connected, it simply missed, as if reality itself didn't want to bother him.

"Impossible…" Shinobu whispered, her breath coming fast. "I can't even touch him."

---

Final Phase: Strength Test

Finally, it was Gyomei Himejima's turn — the strongest physically among the Hashira. Towering over everyone, the Stone Hashira raised his massive spiked flail, muscles rippling.

"Prepare yourself," Gyomei intoned solemnly.

He swung with all his might — an earth-shattering strike capable of pulverizing boulders.

Saitama caught the flail one-handed, barely glancing at it. "Huh. That's heavy."

Gyomei's entire body shook with shock. "This strength… it's beyond comprehension."

---

Aftermath

The Hashira stood in stunned silence. All the legends they'd built their lives upon — training, breathing arts, weapon mastery — felt like children's games next to this bald man.

"Well," Saitama said, clapping his hands together. "That was fun, I guess. Can I go eat now?"

"Wait!" Mitsuri blurted out. "You have to officially join the Corps! We need you!"

Saitama scratched his head. "Eh… I'm not really into organizations. Too much paperwork."

"But you saved us," Zenitsu whined. "You can't just leave after showing off like that! That's so unfair!"

Inosuke, who had been surprisingly quiet until now, suddenly leaped forward. "BALDY! FIGHT ME RIGHT NOW! I'M THE STRONGEST HERE! IF I BEAT YOU, YOU HAVE TO JOIN US!"

Saitama blinked. "Uh… I don't really—"

Before Saitama could even finish, Inosuke launched a flurry of wild, unpredictable slashes with his twin serrated swords, each attack carrying raw feral energy. His Beast Breathing roared through the air like a storm.

Saitama, still unmoving, casually raised a single hand and caught both of Inosuke's swords in his palm — stopping him cold. Inosuke's arms trembled against the immovable force.

"Strong…" Inosuke muttered, teeth bared in awe and frustration.

"You're pretty good," Saitama said. "But, you know, I'm not really into joining groups."

The Hashira huddled together for a quick emergency meeting, whispering like desperate war generals. After a few moments, Mitsuri and Rengoku turned around with sparkling eyes.

"Then we'll make a deal!" Mitsuri declared, bouncing with excitement. "You don't have to officially join, but you can be our Special Honorary Bald Slayer! No paperwork! Just show up when we need you!"

Saitama scratched his head. "Honorary Bald Slayer? That sounds kinda weird."

"It's super flashy!" Tengen insisted. "And only you can pull off that title."

Saitama sighed, realizing there was no escaping their enthusiasm. "Fine, fine. But only if you feed me. I'm starving."

"DEAL!" the Hashira shouted in unison.

---

Feast After Training

Moments later, the entire Demon Slayer Corps was gathered at a long wooden table, bowls stacked high with ramen, rice, grilled fish, vegetables, and even sweet dumplings. The kitchen had gone into overdrive preparing for Saitama's legendary appetite.

As expected, Saitama's eating speed stunned everyone. Bowls vanished faster than anyone could follow, noodles inhaled like air, broth drained as if his stomach was a bottomless void.

"How… how does his stomach even work?" Kanao whispered to Shinobu, eyes wide.

"I'm more scared of this than his strength," Shinobu replied, watching Saitama dunk an entire grilled fish into his ramen like a piece of tempura.

Rengoku laughed with admiration. "His appetite burns with the intensity of the sun itself! TRULY MARVELOUS!"

Even Gyomei, who usually remained calm and serious, seemed unsettled. "This level of consumption… it's beyond human."

Zenitsu, trembling with anxiety, muttered, "He's not a demon, right? Right?!"

When Saitama finally put down his chopsticks, dozens of empty bowls surrounded him like trophies from a victorious battle. He leaned back, patting his stomach contentedly. "Okay. I'll help you guys out if things get bad. Just call me."

The Hashira, now fully convinced that this bald man was a gift from the heavens (or a terrifying anomaly sent to humble their pride), stood and bowed deeply.

"Thank you, Saitama-san," Giyu said quietly. "With you, our chances against Muzan have greatly improved."

Saitama just waved it off. "Eh, don't worry about it. If you need me, I'll be around. Just don't expect me to remember anyone's name."

With that, the first day of the Hashira Training Arc ended not with blood, sweat, and tears — but with an empty kitchen and a full Saitama.

The true training… was about to begin.

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End of Chapter 73