The world around them remained frozen — trees locked mid-sway, Hashira caught mid-breath, swords hanging in the air like suspended silver threads. Only two figures moved freely in this eerie silence: Rokuro, Upper Moon Four, and Saitama, the caped enigma who had crashed into this world like a bald comet.
Rokuro's smile trembled as she took a step back. "This... this isn't possible. No one can resist my temporal domain."
Saitama scratched his cheek, looking around. "Are we… supposed to be moving in slow motion? Did I break something?"
"You're not affected because… you don't belong here," Rokuro muttered, her mind racing. "Your existence disrupts the flow of this world."
"Cool story," Saitama shrugged. "Anyway, are you the villain? Should I punch you?"
Rokuro's eye twitched. "You think you can—"
BAM
Before she could finish, Saitama flicked her forehead. The air cracked like thunder, and Rokuro was sent skidding backward, crashing through two frozen trees before she could even scream. The force was enough to restart her own powers — the air rippled and time surged back to normal.
The Hashira gasped, swords clashing again as the suspended battle resumed. Tanjiro stumbled, disoriented. "W-what just happened?"
"Enemy attack!" Rengoku roared, flames bursting from his blade. "Form up!"
Rokuro stood up slowly, her nose bleeding, her eyes wide with disbelief. "How… how strong is this man?"
"Not very," Saitama said bluntly. "I barely touched you."
That was enough to shatter her confidence.
---
The Hashira vs. Time
Rokuro wasn't done. She slammed her hand into the ground, and the earth beneath the Hashira warped. Sections of the battlefield sped up while others slowed down. Giyu found his sword swing dragging unnaturally, while Sanemi's feet moved like they were sliding on ice at high speed.
"This power is tricky!" Mitsuri called out, her whip-sword flickering between blindingly fast and painfully slow. "She's manipulating time flow around us!"
"Adapt!" Rengoku shouted, flames surging around him. "We are Hashira! We overcome!"
Zenitsu, already trembling, suddenly found himself stuck in slow motion — even his breathing thunder couldn't activate properly.
"THIS IS A NIGHTMARE!" he screamed, his voice stretching like melting wax.
---
Saitama Steps In
"Hold up." Saitama walked forward, totally unaffected by the distorted time zones. He grabbed Mitsuri's sword mid-swing and placed it gently back in her hand. "This is too complicated. Can't we just punch her?"
"It's not that simple!" Tanjiro protested. "She's Upper Moon Four! Her Blood Demon Art controls—"
POW
Saitama casually punched Rokuro straight in the face. She flew upward, her body spinning like a broken doll before slamming into the ground with a crater-forming impact. For a moment, all the time distortions vanished.
Everyone froze.
"...Is she dead?" Inosuke asked.
"She's Upper Moon Four," Giyu said grimly. "It won't be that easy."
Sure enough, Rokuro's body shuddered. She staggered to her feet, her jaw visibly dislocated, but regenerating rapidly. Her eyes were wild with fury — and fear. "What… ARE you?"
Saitama cracked his neck. "Just a guy who's a hero for fun."
Rokuro's entire body trembled. "You… you broke my technique without even trying…"
"Yeah." Saitama looked around. "You're kinda messing up their training camp, so can you leave?"
"LEAVE?!" Rokuro screamed, her powers surging. "I AM UPPER MOON FOUR! YOU CAN'T JUST ASK ME TO LEAVE LIKE A MISBEHAVING CHILD!"
Saitama sighed. "Fine."
Serious Series: Serious Slap.
He didn't even punch. Just a casual backhand slap — but the force behind it collapsed the air itself, sending Rokuro flying so fast that her body broke the sound barrier three times before vanishing over the distant mountains.
A few leaves floated down gently.
Everyone stared at Saitama in utter silence.
"...Did you just slap an Upper Moon into orbit?" Sanemi finally asked.
Saitama shrugged. "She'll probably come back. They always do."
"That… that's not how demon slaying works," Tanjiro said weakly.
Saitama blinked. "It's not?"
---
Rokuro's Fate
Far, far away, Rokuro's battered body lay half-buried in a crater. Her limbs twitched, her pride shattered into pieces smaller than her bones.
"I… I have to tell Muzan," she wheezed. "This… thing… is unstoppable."
Her time powers flickered weakly as she crawled back into the shadows.
---
Night Falls Again
Back at camp, the Hashira sat in a circle around the campfire, staring at Saitama like he was some ancient god who had descended to Earth. Saitama, meanwhile, was roasting a sweet potato.
"So… what's next?" Saitama asked casually.
Rengoku laughed. "Next… we learn. From you."
Saitama blinked. "Oh. Uh… okay?"
Giyu spoke quietly. "If we can survive your training… Muzan won't stand a chance."
Saitama took a bite of his potato. "Cool."
The Hashira all exchanged determined glances. The training camp had just turned into survival training — against the strongest force they'd ever encountered.
---
End of Chapter 40