Chapter 1: The Black Cube in the Warehouse
"Ugh..."
My head felt like it was splitting open.
A brutal hangover.
"What kind of booze did that girl chug like water..."
I fumbled for my smartphone.
It was already broad daylight.
I pushed open the door and staggered into the living room.
"Oh, Peace, you're up?"
My stepmom, Lee Seol-ah, sat on the sofa and looked at me with concern.
"Yes..."
"You really should drink in moderation. Is your stomach okay?"
"I'm dying here. I'll grab some water."
My stepsister, Eun-ha, who was sitting nearby, glanced at me and clicked her tongue.
"Tch. Thought you'd sleep forever. Guess your thread of life hasn't snapped yet."
"Shut it. Is that any way to talk to your oppa?"
"Oppa? In your dreams."
I pulled some water from the fridge and chugged it down.
Felt alive again.
I wiped my mouth and shot a sidelong glare at the two of them.
These people had taken in a stray like me—no drop of blood between us.
On the surface, I played the sweet, obedient son.
But inside?
Black rot, festering through and through.
Every day, I fantasized about crushing their dazzling, arrogant goodwill.
Forcing them to grovel in the dirt at my feet, broken and ruined.
"Ah, Peace. You remember you're supposed to clear out the warehouse today, right?"
"Oh. Yeah."
"I know it's a hassle, but just handle that. I'll clean up later."
"Got it. I'll do it now."
The warehouse was pitch dark.
I shoved aside crates, choking on the musty dust.
Thud.
"Huh?"
An old box tipped over, spilling junk everywhere.
Flashy trinkets mixed with worn diaries and such.
"Mom's stuff from her active days."
I'd known for a while that my stepmom was a retired magical girl—a legend from decades ago.
These days, relics were gone, monsters popped up rarely, and magical girls were treated like idols.
Back then? Real life-or-death stakes.
"Huh? What's this?"
Amid the mess, a pitch-black rectangular crystal gleamed unnaturally.
No barcode. It just... pulled at my eyes.
"......"
The moment I picked it up, a bizarre vibration hit me.
An intense, inexplicable pull—like a living heartbeat.
"Whatever it is, it's pretty slick-looking."
I pocketed the black cube, entranced.
Finished sorting the rest and headed back to the living room.
"Mom, warehouse is all cleared."
"Good job. Huh? What's that bulge in your pocket, sweetie?"
I pulled out the black square and showed her.
"Found it rolling around in a corner box. From your magical girl days?"
"Hm? Let me see..."
Lee Seol-ah tilted her head, rummaging through memories.
"Oh, that! A fragment I picked up during a relic dive ages ago."
"Can I keep it as room decor? The black's kinda cool."
"Sure, why not. We ran every magic scan on it back then—no reaction. Total empty shell. Safe as houses."
"Thanks."
Safety confirmed.
I grinned and slipped back to my room.
Shut the door, set the black cube on my desk.
Clatter! Rattle rattle!
"Wha—huh?"
The cube started thrashing wildly.
Then pitch-black smoke billowed out, forming a grotesque mascot shape in midair.
[—Oh ho. Finally awake.]
"What the hell are you? Hologram?"
[Insolent whelp! I am the Guide of the Monster King!]
"Monster King?"
[Indeed. You possess the qualities of the Monster King, lost to history. Contract with me—gain the power to bring ruin to the world!]
A slimy, sinister vibe—the polar opposite of those cute magical girl mascots.
I yawned and waved it off.
"Nah, pass. Not interested."
[......What?]
"World destruction? Too much hassle. I just wanna live normally. Get back in your box."
Silence hung heavy.
Then the black mascot clutched its gut and cackled.
[Kuhahaha! Normally? I've seen that slimy, ugly lust for domination inside you!]
"......"
[Playing the good son on the outside, but dying to make those bitches kneel at your feet, eh? Shall I expose every filthy desire?]
Its mockery chilled my gaze to ice.
No need for pretense here.
"...Sigh. Busted."
[Hm?]
"Look, that's not what I want. I'm not into destruction."
[Worry not! The true power of the Monster King is no such thing.]
"Then what?"
[This power manifests solely through the contractor's imagination.]
"Imagination?"
[Aye. Past inheritors lusted only for raw strength, imagining brute beasts—and birthed mindless monsters.]
"Hm. I see."
[I'm the last Guide left on Earth. You are my final hope.]
"Now that's different. Quit yapping and hand over the power."
[Kuhaha! I like you! Very well—receive power befitting your vile nature!]
KABOOM—!
The black mascot poured power into me and vanished.
Black light surged through my body.
[Reconstructing into the Monster King's physique.]
Explosive vitality swirled inside.
My average body reshaped: slim on the outside, but packed with taut, overwhelming steel-like muscle.
And the heat boiling in my lower gut? Far from ordinary.
"Ha. Beastly stamina overflowing. Perfect."
The Monster King's power bends to imagination.
I don't want mere destruction.
I want the one weapon to utterly ravage and dominate those arrogant women.
As the light faded, my hand held a sleek, pitch-black VR visor of smooth curves.
◈ Forced Domination: Slip onto target's face—bypasses all magic resistance, seizes brainwashing control in under 3 seconds.
◈ Vision Assist: Front turns semi-transparent during command execution for wearer visibility.
◈ Memory Wipe & Imprint: Removal erases all session memories. Body retains overwhelming pleasure imprints from domination, triggering gradual corruption (bitchification).
"Insane. Specs are legit."
The perfect weapon.
I smirked wickedly, thumb hovering over the visor's switch.
Click.
Vrrr—!
Power on—thick vibration thrummed through my fingers.
No magic leaked out.
Really looks like a normal gadget. Camouflage is top-tier.
Bang!
The door flew open without warning.
"Hey. If you're not sleeping, come to the living room for fruit."
Eun-ha.
She barged in with an annoyed scowl—then her eyes locked on my hand.
"What's that? VR gear?"
"Yeah. Found it in the warehouse earlier."
"You pick up anything. It broken?"
"Nah, works fine. Wanna try?"
I grinned, thrusting the device toward her.
"You're nuts? You enjoy it yourself. I'm heading out—kya?!"
As she turned to leave.
My reconstructed body lunged like a beast.
"Where you going."
"Let go! Mmph?!"
I snatched her arm mid-stride and slammed her onto the bed.
Overwhelming strength I'd never dreamed of before.
No chance for resistance—I slapped the visor over her face.
Ziiing—!
"G-get this off... Ahh!"
Her back arched like a bow as she thrashed.
Fierce resistance.
But it didn't last three seconds.
"Haa... aaah......"
Eun-ha's body went limp.
Only dazed moans filled the room.
Perfect brainwashing.
Won't carry to the living room, right?
I lightly patted her cheek.
"Eun-ha. Hear my voice?"
"...Yes. I hear you..."
Mechanical
Mechanical, emotionless reply.
The stepsister who'd treated me like a bug? Gone.
How deep does the brainwashing go?
I tested the limits.
"Tell me your biggest secret from the family."
"...I am... a magical girl."
"......What?"
I doubted my ears.
"Two months ago, contracted with a pink mascot. Rookie active duty."
Ex-magical girl stepmom.
Active rookie magical girl stepsister.
"This family's a riot."
I let out a disbelieving chuckle.
"Why hide from family?"
"Get famous... earn big money... then surprise reveal."
Idiot.
But perfect for me.
Active magical girl? Ideal test subject.
"Eun-ha."
"...Yes, Master."
"Take off your top."
"...As you command."
Smooth.
No hesitation. She stripped off her top.
Perfect domination—no shred of shame.
Solid performance.
Go all the way?
But Lee Seol-ah in the living room nagged at me.
"Stop. Put your clothes back on."
"......Yes."
I inwardly cheered as she dressed.
Before wiping memories, plant some insurance.
"From now on, when I whisper 'good sister' in your ear."
"......"
"You snap straight into perfect slave mode. Got it?"
"...Understood."
"Good sister."
"...Hearing those words pulls me into Master's slave......"
Setup complete.
Now, wherever she is, those four words turn her into my groveling bitch.
Click.
Power off—I yanked the visor free.
Her eyes snapped back to focus.
No gap—the rebellion picked up seamlessly.
"...Get it off already?! You're insane?!"
Thud!
She shoved my chest hard and bolted up from the bed.
The brainwashing? Erased white.
Time jumped straight from when I forced the device on her.
"Why jump me outta nowhere! You lost it?!"
"Hey, I was just sharing something cool. Why freak?"
"Told you I don't want your crappy VR! Ugh, damn... annoying."
I played innocent, flashing a sleazy grin.
"No need to hate it that much."
"Eww, total gross-out. Look at my clothes, all wrinkled."
She huffed, roughly straightening her outfit.
Then—wobble—she gripped the bed edge.
"You okay?"
"Huh? No..."
"Something hurt?"
"Why's my leg suddenly... no strength..."
She tilted her head, touching her forehead.
Cheeks faintly flushed, like a low fever.
Memories gone, but body remembers.
Residue from the brain-scraping domination.
No full breaking yet, but enough to plant corruption seeds.
"Your room got the heater cranked? Why's it so hot..."
"Nah. You just worked up a sweat raging."
"Maybe I'm coming down with something from overdoing it... Ugh, whatever!"
"You go first. Be right there."
"Hurry to the living room! Mom wants fruit!"
She shook her head wildly and fled the room.
Slam.
Door shut. Alone now.
"Hahaha......"
I caressed the cold visor in my hand.
First test: smashing success.
Next up.
I opened the door to the living room.
My lips curled in a cruel smirk.
The noble ex-magical girl on the sofa.