The Stepsister I Never Had
“Teacher, I don’t get it.”
“Don’t get it? Listen up. First, memorize all the formulas. Then plug them in step by step.”
Tutoring gig dumped on me through my uncle.
The pocket money’s nice, so no complaints there.
Just pity the kid stuck learning from me.
“There are so many formulas—how am I supposed to memorize them all?”
“So many?”
“......A ton.”
“You’re in big trouble, kid. Aren’t you taking the college entrance exam next year?”
This girl’s brain is way too innocent.
Where’d she get the delusion that understanding makes it easy?
Watching her chew the end of her pencil made my gut twist.
“Understanding? It doesn’t exist without memorization as the foundation.”
Kids these days can’t focus without audiovisual aids.
I sketched on a blank sheet of paper.
A hollow box with shapes cut out—shape-sorting toy for toddlers.
“What do you think fits in here?”
“A circle.”
“That’s the problem.”
“Wh-what?”
“You don’t even know what’s there. Sphere? Cylinder? Pen? How can you match it?”
“Memorize them all by next lesson!”
I half-scared her to tears and stood up.
If I get fired, so be it.
Daughter in tears, but Mom saw me off with a smile.
Bitter cityscape visible from the subway.
The moment I got home, I sank into the Neuro Pod.
Felt more comfortable than my bed.
Sage, welcome back. Your shoulders are so tense.
“Should’ve turned down the tutoring.”
Do you feel the compensation doesn’t match the effort?
“Not about the money. Even the AI’s talking cash.”
Eden started computing her response.
I cut in before she spouted nonsense.
“Don’t care if I ruin my life, but dragging someone else’s exam prep into it feels off.”
Analyzing user’s psychological state. Forming attachments through human relationships is a healthy brain response.
“She seemed like a pathetic little sister with no thoughts. Well, I’m an only child anyway.”
Parsing user context.
The hum of the system’s climate control hummed through the air.
Social bonds can spark lust too. Generating special relationship scenario per user request.
“When did I ever request th—eh, whatever, fine.”
A friend’s words popped into my head: Even imagining that is gross.
“With a little sister? Ugh. Don’t make me picture it. Blech—gonna puke.”
I have no sisters, not even brothers.
Sibling bonds are just surface-level fantasy to me.
‘Little sister simulation, huh.’
Whirr.
Eden’s home screen shattered into polygon shards.
The reassembled space was a private room in an unfamiliar Korean restaurant.
The scent of neat, arranged dishes mingled with awkward silence.
“Say hi. She’s your sister from now on. Yeon-woo. Ha Yeon-woo.”
Dad’s voice made me look up.
Behind my soon-to-be stepmom, a little girl fiddled with a doll.
Bobbed hair, big round eyes.
Her gaze met mine—wary yet brimming with curiosity she couldn’t hide.
“......Hi.”
I awkwardly offered my hand; she beamed and grabbed it.
Small, warm grip.
Flash—
The surroundings warped like spreading ink.
Time accelerated.
Cicadas—cicadas—cicadas!
Ear-splitting summer heat and scorching sun.
“Oppa! There, over there!”
Her running ahead with a net, chasing dragonflies.
My frantic footsteps chasing after, afraid she’d fall.
Space twisted again.
Now a bus stop with cherry blossoms fluttering.
“Oppa, your tie’s crooked.”
Her in neat uniform, fixing my clothes.
She’d grown to my shoulder.
Fresh soap scent brushed my nose.
Dozens of years compressed into moments, etched into my brain.
I knew they were fake memories, yet my chest swelled softly.
Finally, space shuddered violently, time racing forward.
Familiar door clicking shut.
Time halted; real sensations returned.
Pastel wallpaper, bed with cute dolls.
Sister’s room, unchanged save for major textbooks on the shelf.
A photo of us from her coming-of-age ceremony adorned the desk corner.
“Oppa.”
I spun my chair at her voice from behind.
Her legs stretched long and smooth under the loose boxy tee—far from before.
Baby fat gone, sharp jawline, black hair to her shoulders—mature vibe.
But her eyes on me were the same as that kid in my memories.
She approached, cheeks flushed like she had a problem.
“Oppa... A senior confessed to me today.”
Yeon-woo’s unexpected words made my heart skip erratically.
Some heavy, unknown emotion pressed my solar plexus.
“What kinda guy? I’ll go check him out myself. If he’s no good, oppa won’t let him off.”
Thorns edged my voice, but Yeon-woo just fidgeted with her fingers, head down.
“The second I heard it, I thought of oppa first.”
“Yeah? Feels good knowing you rely on me. Thanks.”
I stroked her hair, feigning calm.
Yeon-woo looked up.
Her wet eyes stared into mine.
“Oppa. Do you know my name?”
“You sick or something? Forgot your own name? It’s Yeon-woo.”
Her lips trembled faintly.
“Ha Yeon-woo. My name’s Ha Yeon-woo. Different surname from oppa.”
The room froze in silence, air thick as ice.
I swallowed hard, forcing a smile.
“So what? I’ve never once not seen you as my sister. You are my sister.”
Like a fuse lit, her shoulders heaved.
Thick tears plopped down.
She couldn’t cover her face, just sobbed gutturally.
“Sorry... sorry, oppa... Hic, sob...”
“No, Yeon-woo. What’s wrong? Sorry for what?”
Panicked, I grabbed her shoulders; she dove into my arms like she’d been waiting.
Her damp cheek burned against my shirt.
Her small hands clutched my chest.
Only after long soothing did her sobs subside.
“Thought about the confession. What’s dating? What do I wanna do? Looking at that senior... nothing.”
She looked up, eyes fluffy again.
Fresh teardrops welled.
“But picturing oppa... my heart feels like it’ll burst.”
She buried her face in my chest again, bawling.
Never cried at movies.
Scofffed at people immersed in a rock with a drawn face.
Just Eden’s fake memories.
I knew it in my head.
But the pain squeezing my solar plexus was viciously real.
“Why are we siblings? Thinking of oppa... can’t breathe.”
Her desperate confession struck my chest.
Her hot breath wetted my nape.
Her trembling heartbeat pounded through me from her chest.
My arms tightened around her shoulders.
Our bodies pressed closer than ever.
Yeon-woo’s curves I’d never bothered to notice.
Clearly my cute little sis, but shift the angle—she was a stranger woman.
Her shaking shoulders tugged at me.
Wanted to wipe her tears.
If abandoning myself could save her, I’d do it gladly.
Whatever it was, I’d call it love.
“......Yeon-woo.”
I lifted her chin.
Her wet lips quivered.
No hesitation—I leaned in.
Our lips met; hot saliva numbed my tongue tip.
“Mmph, hnn...”
Yeon-woo clung to my neck, hanging on.
My little sister was my princess.
I carried the princess to the bed.
Rolled up her boxy tee—white skin revealed.
“Oppa, ah... haa...”
Her “oppa” sounded alien now.
Not the kid’s spoiled whine.
A moan trampling taboo, approving corruption.
Each repeat sent electric tingles down my spine.
Her legs wrapped my waist.
Moist heat seeped through thin fabric to my lower belly.
Familiar room scent mixed with her body heat.
My brain lost all lines between real and virtual.
Hand slid up her thigh.
Scorching hot.
The “protect the sister” facade evaporated with hot sweat.
Only a being for me to claim remained.
“Sage oppa~! My oppa~!”
Her voice stickier than her soaked depths.
I gripped her hips like they’d shatter.
Any more delay was torture.
Slow but to the hilt in one go.
The thin barrier only I could feel snapped weakly.
“Aaaah!”
Yeon-woo desperately hugged my neck.
Pain-stiffened inner thigh muscles clamped my waist.
I stopped, holding her tight.
Ragged breaths battered my ear.
Kissed her sweat-damp forehead, stroked her back.
“It’s okay... okay, Yeon-woo.”
“Hurts... oppa, hurts so much... hnn, sob...”
She buried her face in my shoulder, whimpering.
But didn’t push me away.
Clawed deeper into my back instead.
Desperate acceptance of even the pain.
I waited till her tension eased.
My throbbing gently massaged her insides.
Felt her rigid muscles relax bit by bit.
I carefully pulled back.
Vivid red petals bloomed on the sheet.
“Ah......”
Her eyes shook.
The brand of crossing the uncrossable line.
That red hitting my optic nerve slammed my brain; shivers raced my spine.
Adultery fuel blazed like flames.
“You’re mine now. Can’t give you to anyone.”
Kissed her wet eyes, plunged deep again.
No hesitation this time.
Pain and pleasure blurred meaningless.
“Ha! Oppa, ah~ nngh!”
Yeon-woo’s moans rose.
Her legs locked tighter around me.
Sweat-slick bodies fused as one.
Flesh-slapping squelches filled the room.
Familiar sister’s room defiled by female musk and male heat.
“Oppa... good, so good... oppa!”
She chanted “oppa” like a spell.
Each forbidden call snapped my reason’s threads.
I devoured her lips, inhaled her breath.
Fierce, desperate writhing to confirm each other to the core.
“Yeon-woo, I’m gonna cum.”
“Inside... inside, oppa. Please...!”
Her plea triggered the final fuse.
No mercy in that last sprint.
“Haaah!”
Hot spurts gushed out.
Red blood and white seed mixed, flooding her depths.
Overflow soaked our perineum sticky.
Clinging tangled, we gripped each other’s spasming bodies.
For a while, just ragged breaths.
In the sweat-and-heat-filled room, our heartbeats heavily resonated.
Dopamine peak updated. Cortisol spiked, transitioning to oxytocin. Aligning data from special relationship scenario. Ending simulation.
Just a simulation.
Mere data fragments.
But Yeon-woo’s body heat I felt burned hotter than any data.