Chapter 5: Muzan’s Nightmare and Baldy’s Breathing Training

Far away from the Demon Slayer headquarters, deep within an underground lair pulsing with malevolent energy, Muzan Kibutsuji sat on his throne, fingers tapping the armrest in irritation. His usual arrogance was nowhere to be seen. Instead, for the first time in centuries, he felt unsettled.

A crow had delivered the news — Upper Moon Five, Gyokko, reduced to fish paste with a single slap.

Muzan's hands trembled slightly as he recalled the image the crow described. A bald man in a ridiculous yellow outfit. A man with no Breathing Technique, no Blood Demon Art, no Nichirin blade — yet capable of effortlessly erasing an Upper Moon.

"This is a problem," Muzan muttered.

The remaining Upper Moons gathered before him. Doma smiled, but even his ever-present grin twitched nervously. Akaza clenched his fists, feeling something he rarely felt — doubt. If a mere human could erase an Upper Moon with such ease, what did that mean for demons as a whole?

"Shall I go next, Lord Muzan?" Kokushibo, the strongest Upper Moon, asked calmly.

"No." Muzan's crimson eyes gleamed. "Not yet. First, we must adapt."

With a wave of his hand, the air rippled. From the shadows emerged new figures, demons who had once perished at the hands of Demon Slayers but were now reborn — stronger, fused with experimental Blood Demon Arts stolen from other demons Muzan had consumed.

"Let me introduce our newest creations," Muzan announced. "The Hybrid Moons — demons built specifically to overwhelm any human, even that bald freak."

The demons stepped forward — Kagenami, Enmara, Shizanken, and others, each more twisted than the last. Their power was palpable, making even Akaza glance at them warily.

"This 'Saitama'," Muzan said, spitting the name like venom, "will learn that no matter how strong one's punch is, there are things far beyond brute strength."

Muzan's wicked smile returned. "Prepare for war."

---

Meanwhile, back at Demon Slayer HQ…

Saitama stood in the middle of a grassy training ground, his white cape fluttering in the breeze. The Hashira, lined up in front of him, had decided that if Saitama was going to stay at headquarters, he should at least learn proper Breathing Techniques.

"Alright, Baldy!" Rengoku's voice boomed. "Let's find your Breath Style! Every Demon Slayer has one!"

"Breath?" Saitama blinked. "I'm already breathing."

"That's not what we mean!" Mitsuri giggled. "It's a special way to control your breathing to enhance your body and sword techniques!"

"I don't have a sword," Saitama pointed out.

"Then take this!" Tengen tossed him a spare Nichirin sword. Saitama caught it with one hand, staring at the blade.

"Feels flimsy," he said, bending it slightly between his fingers like a piece of wire.

The Hashira twitched.

"Okay! First step," Tanjiro said nervously, trying to be the peacekeeper. "Take a deep breath, focus your mind, and visualize your element!"

"My element?" Saitama asked. "Like what?"

"Fire, water, stone, wind — something that fits your soul!" Tanjiro explained earnestly.

Saitama closed his eyes for a moment. The Hashira leaned forward, curious.

"Okay," Saitama said. "I've got it."

"What is it?" asked Mitsuri, eyes sparkling.

"Breath of Sale Discount."

The silence was deafening.

"…What?" Giyu finally broke the silence.

"You know," Saitama shrugged. "That feeling when you find a limited-time 90% off sale on groceries. Heart rate spikes. Blood rushes. Total focus."

The Hashira stood speechless. Even Muichiro, usually half-asleep, blinked several times.

"That's not a real Breath Style!" Sanemi shouted. "Are you mocking us?!"

"No, it's real," Saitama insisted. "It's the only time I feel truly alive."

Tengen sighed, rubbing his temples. "Okay, forget that. Let's see you try a real Breath Technique. Copy me."

He demonstrated Sound Breathing, his twin blades slashing through the air with explosive force. "Your turn."

Saitama sighed, holding the Nichirin sword awkwardly. He gave it a half-hearted swing.

CRACK!

The sword shattered instantly.

The Hashira nearly fainted.

"This metal's really weak," Saitama said, frowning. "You guys should try tungsten or something."

"Enough of this!" Sanemi's patience snapped. "You can't fight demons with bare hands! That's not how our world works!"

"But I already did," Saitama said.

"And you're going to learn to do it our way!" Sanemi roared.

"Why?" Saitama asked, genuinely confused. "Your way looks slow and complicated."

Sanemi lunged, fist raised — only for Saitama to step slightly aside. Sanemi tripped over a rock and faceplanted into the dirt.

"See?" Saitama shrugged. "Complicated."

Before Sanemi could rise, a crow swooped down, its voice urgent. "Urgent message! Lower Moon Five Kogai, revived and upgraded by Lord Muzan, is attacking a nearby village!"

"Perfect!" Rengoku declared. "We'll send Baldy to test his skills!"

"Why me?" Saitama asked.

"Because if you're as strong as they say, this will be nothing for you!" Rengoku grinned.

"Plus," Tengen added, "you've got that Breathtaking Sale Discount Technique, right?"

The Hashira burst into laughter. Saitama sighed, scratching his bald head. "Fine, I'll go. Maybe I can finish fast and still catch the evening sale."

As he walked off, Tanjiro followed, anxious. "Saitama-san, are you sure about this? This demon might be stronger than Gyokko."

"Doesn't matter," Saitama said. "Strong or weak, it's still just a punch."

Tanjiro gulped. He wasn't sure if he was walking beside humanity's savior or its biggest problem.

---

End of Chapter 5