Flashbang Takedown and the Accelerated Apocalypse

The knights burst through with a crack!Crunch! The wooden door split in half, revealing the silhouette of a knight shrouded in blue aura. With a blank expression, I pulled the pin on a 9-Bang flashbang and casually tossed it through the gap.

"Romance fantasy knights. Time to taste some modern light and salt."

Roll, roll, roll. The black metal cylinder tumbled across the dim sewage floor. The Imperial Knight Captain, smashing through the door, glanced down at his feet. The blue Aura ‍‍‌‌⁠​​⁠‌​​‍​​‍​‌​⁠‍‌‍⁠⁠‌⁠‌‍‌‍‌‌‌‍⁠​‌​‌​‌‍‌‌‌⁠‍​​‌‍⁠‌‌⁠⁠enveloping his body lit up the dark underground passage like broad daylight—radiant and intimidating.

In this romance fantasy world, an Aura Master was a walking tactical weapon, an absolute shield that shrugged off physical blows and low-level magic.

The captain sneered at the small metal lump by his foot. "Ha! Cornered rat, resorting to crude darts. You think that toy will work against my aura blade?!"

He didn't even consider dodging. Why would he? In their worldview, forged by a lifetime of swords and mana, a mana-less hunk of metal like that was just shrapnel, harmless even if it exploded against their aura shield.

That arrogance sealed their fate.

In the brief moment he spat his line, I'd already donned my prepped 3M Peltor tactical headset from inventory ‍‍‌‌⁠​​⁠‌​​‍​​‍​‌​⁠‍‌‍⁠⁠‌⁠‌‍‌‍‌‌‌‍⁠​‌​‌​‌‍‌‌‌⁠‍​​‌‍⁠‌‌⁠⁠and squeezed my eyes shut.

The superhuman ability called aura had one fatal physical weakness: concentration. Circulating mana from the dantian throughout the body required advanced breathing and mental focus. Disrupt that forcibly?

Even a Sword Master’s aura scattered in an instant. And modern tactical gear was specialized for shattering that flimsy human "focus."

BOOM-BOOM-BOOM-BOOM-BOOM-BOOM-BOOM-BOOM-BOOM-!!!

Not a single blast. Nine consecutive explosions at 0.5-second intervals: 170 decibels of deafening roar and a murderous 7 million candela flash.

This wasn't a weapon that tore flesh with shrapnel. It physically "shut down" the optic nerve, auditory cells, and vestibular system for balance—a sensory assault.

In the sealed concrete and bedrock sewage tunnel, the flashbang's power amplified dozens of times worse than outdoors. Light ricocheted off walls, searing retinas even through closed eyelids. The blasts hammered eardrums and rattled brains.

"Gaaahhh—!!!"

"My eyes! My eyyyyyes!"

"Ears...! Gahk, hack!"

The captain and his two elite knights, aura blazing moments ago, dropped their weapons and writhed on the floor. Their brilliant blue auras had flickered and faded after just three bursts, breathing disrupted.

No human could control mana amid simultaneous blindness, deafness, and vertigo-induced vomiting.

With my headset's external noise cancellation on, I strolled out through the acrid gunpowder haze.

If I'd lobbed in a thermobaric grenade and turned them into meat pie?

A red System warning would flood my vision, triggering the World's Compulsion Force. Killing named Imperial Knights—key original plot forces—would freeze my lifeline System shop for a month minimum.

But I didn't kill them. Just temporary sensory blackout. Perfectly legal self-defense within plot plausibility.

"Ugh... y-you... what black magic...!"

The captain staggered up, eyes unfocused, groping air. With only faint aura flickering, he was just a blind, deaf neighborhood uncle in heavy metal armor.

No reply. Instead, I racked the pump on my M870 pump-action shotgun.

Clack! Crisp chambering of the 12-gauge beanbag round.

Beanbag round: Kevlar pouch packed with lead shot. Non-lethal crowd control. Won't pierce flesh, but hits like a flying sledgehammer to the solar plexus.

I aimed at the captain's solar plexus—gap in his breastplate—and pulled the trigger.

Bang!

"Gaaaargh—!!!"

A dull thud, body bending like a bow. Blood-mixed vomit sprayed. At least three ribs cracked.

The 100kg+ brute crumpled, gasping from one rubber slug.

No hesitation. Rack, fire. Rack, fire.

Clack, bang! "Grahk!"

Clack, bang! "Mercy... gahk!"

Three seconds. The two staggering elites took knees and solar plexus hits, splashing into sewage filth.

The Empire's top fighting force, neutralized by three shots from a mana-ignorant commoner.

I lowered the barrel, removed my headset. Ringing filled the sewer; elites twitched like bugs, groaning.

"Why smash someone else's door, huh?"

Tsking, I approached the captain and picked up his fallen blue-glowing longsword.

"Oh ho."

A grin spread. I nudged the captain's body with my boot, unbuckling his silver breastplate.

"This mithril alloy, right? Romance knights got cash to burn. Slapping pricey metal on decorative junk."

"Y-you... dare touch the Imperial... ugh!"

"Yeah, yeah. Save the Imperial glory crap for sewer rats. Heave-ho."

I stripped his breastplate, shoved it in inventory. Then the two elites' swords, armor, mana stone rings, gold belts. Two minutes to sweep it all like a ragpicker.

Shivering in underwear and thin tunics, I booted them out through the shattered door into the sewage ‍‍‌‌⁠​​⁠‌​​‍​​‍​‌​⁠‍‌‍⁠⁠‌⁠‌‍‌‍‌‌‌‍⁠​‌​‌​‌‍‌‌‌⁠‍​​‌‍⁠‌‌⁠⁠passage.

"Business done. Get out. Private property now—trespass next time, I'll load buckshot."

Shooing them, I spent SP on a 30cm-thick steel door replacement, slamming it shut.

Screeech—thud! Heavy friction, locks engaging echoed inside.

"Phew. Clean."

Wiping sweat, I turned.

And there she was.

"Y-you... what... are you...?"

Ayla Erzen, Duke's lady, slumped against the wall. Blasts or terror pierced her sedative coma. Red eyes wide with shock stared up, lids heavy with sleep.

Her gaze flicked between my bizarre iron weapon (shotgun) and my impassive face that just stripped and booted the Empire's strongest knight.

"Oh, awake? Potent stuff. Duke's daughter got mental fortitude, huh."

"Stay back, monster...! Mana-less commoner, how'd you take down Kellun Knight Captain...!"

She scrambled back, trembling hands on floor. I wasn't some lucky sewer rat anymore. I was unknown terror shredding common sense and Imperial might.

I shrugged at her freakout, approached.

"Monster? Harsh. Just a law-abiding citizen defending property. And," I snapped fingers by her face—pop! "you're my precious VIP customer who gifted 50,000 SP. So chill, crash in the corner. You paid for bed."

"V... what? SP? What're you—kyaa!"

Ignoring, I grabbed her nape, tossed her onto soft combat ration crates in the corner.

"Be good. Gotta play house now."

She bit lip in fury-fear mix, but lids drooping—she'd crash soon. No more attention.

Heading to the central open space for main control room, I summoned the System window.

"Heh heh. Sweet, so sweet."

62,000 SP. Not just repairs. Capital for an "absolute safe zone" to laugh off low-level mutants while frying spam when apocalypse hit.

Trembling fingers opened System Shop [Architecture/Defense] tab. Level 1 defense from Ayla's stone gleamed.

"System. Upgrade entire outer bunker walls to titanium alloy. Install two 'Auto-Targeting Gatling Turrets (CIWS)' in entrance passage. Basic hydro generator too."

Vrrrrm—!

The entire massive bunker hummed pleasantly. The System's supernatural power reshaping reality.

Rusted, cracked ancient concrete walls crawled with sleek silver-gray titanium plates like living growth. Ceiling pipes renewed, outlets in corners. Entrance ceiling: heavy mechanical whir, two matte-black 6-barrel gatling turrets descended, wiring connected.

"This... a dream...?"

Ayla, huddled in corner, muttered at the miracle unfolding. No mage chant, no mana flow—just mutters at air, transforming ancient ruin to high-tech fortress. Beyond her comprehension.

Mind maxed, her head lolled, back to dreamland.

I stroked the titanium wall, enraptured. Cold metal touch. In one year, when spores descended and magic/divinity tanked, this was my sole perfect power.

"Perfect. Stock more food, spin up hydro, and..."

Satisfaction smiling, planning next—

Beep—!

My blue System hologram flushed blood-red. Cheerful tone twisted to piercing, ominous siren wailing through the bunker.

"...Huh?"

Frowning instinctively, I read the hovering red text.

"Wait, hold up. Selling one mana stone voids mana veins? What bullshit!"

I yelled desperately, but the red warnings ignored, spitting merciless updates.

"What...?"

My pupils quivered. System window top-right: Countdown ticking 1 second at a time since possession, to doom.

Numbers spun roulette-crazy.

365 days. 350. 330. 310. Plummeting nonstop.

My heart pounded in sync.

No. Not ready. Need more food, ammo!

Finally, clunk—stopped.

"......Fuck."

Deflated ‍‍‌‌⁠​​⁠‌​​‍​​‍​‌​⁠‍‌‍⁠⁠‌⁠‌‍‌‍‌‌‌‍⁠​‌​‌​‌‍‌‌‌⁠‍​​‌‍⁠‌‌⁠⁠curse slipped out. Price of 50k SP from the original's key item: apocalypse two months early. Horrific butterfly effect.