Lightning crackled in the far distance, echoing faintly across Mount Natagumo. The sharp scent of ozone mixed with the iron tang of blood and damp soil. I paused mid-step, turning my head slightly toward the direction of the sound.
"That lightning strike…" Tanjiro murmured, his brow furrowed with concern. "That's Zenitsu's attack."
Yuri's eyes darted upward toward the sky, her hand resting on her weapon. "But… there isn't a single thundercloud."
I chuckled softly, brushing a strand of dark hair from my face. "That's because it's not real lightning. People in this world have something called breathing techniques. It's similar to martial arts techniques we use—focused breathing to enhance physical abilities, create illusions, or even emulate natural elements like fire, water, or thunder."
Yuri tilted her head, intrigued. "So, it's more about spiritual energy control through respiration?"
"You could say that." I smiled faintly, gazing at the forest ahead. "Each style represents a philosophy. Thunder, Water, Flame, Beast… They embody their element, not through magic, but through something different."
Tanjiro nodded thoughtfully. "Zenitsu's technique… Thunder Breathing. It looks like lightning but is born purely of movement and focus." His voice softened with concern. "I just hope he's okay."
Inosuke snorted, pounding his chest proudly, his two jagged Nichirin blades gleaming in the dim forest light. "That crybaby? He'll be fine! If he dies, it's because he's weak! I don't need to worry about him!"
Tanjiro frowned at his brash tone. "Inosuke, don't say that. He's our friend."
"Friend?" Inosuke barked a laugh. "The only thing I care about is who's stronger!"
Tanjiro sighed. I could tell he was trying to stay patient. The boy had a kind heart—too kind for a world like this.
We reached a river soon after. The soft murmur of water mingled with the rustling of wind through the spider-web-draped trees. As Tanjiro knelt beside the stream to refill his gourd, he glanced back at Inosuke.
"You're covered in cuts," Tanjiro said worriedly. "Are you sure you can keep going?"
Inosuke immediately puffed up like an offended boar. "Cuts? What cuts!? These are just… markings of my battle prowess!"
Tanjiro blinked. "You're literally bleeding."
Inosuke turned away, crossing his arms defiantly. "I'll never back down! Don't underestimate the great Inosuke Hashibira!"
I couldn't help but smirk. "He reminds me of Cocytus, if Cocytus were a feral child raised by wild boars."
Yuri stifled a laugh behind her hand. "The resemblance is uncanny, my lord."
Before we could continue, Tanjiro's expression shifted—his nose twitching slightly. His eyes narrowed, scanning the treeline. "There's someone nearby…"
Following his gaze, I saw her—pale as moonlight, her white kimono fluttering as she stood just across the river. Her eyes glowed faintly in the mist, filled with both fear and malice. A demon.
"She's… small," Yuri murmured, studying the girl. "But her aura isn't weak."
Tanjiro tensed, his hand gripping the hilt of his sword. "I didn't even smell her until now. The scent of demons is so strong across this mountain, it masked hers completely…"
Before anyone could act, Inosuke burst forward, shouting with reckless glee. "You're mine!"
The demon girl flinched and stumbled backward, her lips trembling. "Father!"
That single word froze Inosuke mid-swing. "What did you say?"
The answer came almost instantly.
The forest trembled. Trees cracked and fell like matchsticks as something massive tore through the foliage—an enormous spider-like demon, easily the size of a house. Its grotesque form landed in the river with a crash, sending waves splashing across both banks.
"Don't come near my family!" The creature roared, its many eyes glowing with fury. "Stay away!"
"Now that's a demon," she muttered, stepping forward defensively.
Tanjiro drew his sword, his eyes wide. "That must be the father demon…."
I raised a hand calmly. "Tanjiro, lend me your swords for a moment."
He blinked, confused. "My… swords? Why?"
"Because," I said, turning my gaze toward the towering demon whose arms were thick enough to crush boulders, "I want to test something."
Tanjiro hesitated for a moment before nodding slowly and handing over one of his Nichirin blades. "Be careful. These are meant to kill demons the right way."
I gave him a faint smile. "That's exactly what I want to confirm."
Gripping the sword, I could feel it hum faintly—maybe it was because of the Class Warrior's God. I feel this blade was alive. It was a fascinating weapon, designed to channel human resolve and nature's purity into something that could erase demonic corruption.
"Interesting," I murmured, adjusting my stance.
Father Demon roared again, charging straight toward us, the ground shaking with every step.
Inosuke grinned wildly. "Perfect! A big target!"
Before he could leap, I stepped forward. With a single smooth motion, I vanished—appearing just in front of the monster's descending arm. The Nichirin sword flared in my grasp, its blade shimmering faintly.
I swung once.
The demon's head flew off, dissolving into black ash before it hit the ground.
Tanjiro's eyes widened. "That… that was—"
"Natural," I finished, watching the fading particles drift into the air. "So that's how the system defines it. The Nichirin blade acts as the medium to purify the demon essence."
The notification chimed faintly in my mind.
[Quest Progress: 'Kill Demons by Natural Means' – 1/???]
[Reward: 25 quest Coin]
I smirked. "Finally got something."
Inosuke whooped from behind. "You stole my kill! I'll crush you next!"
I ignored him, instead looking down at the Nichirin sword, admiring its subtle energy. "Yuri, when we get back, remind me that we'll need to forge our own version later."
"As you wish, my lord."
~~~