Chapter Index

    .

    “…Still don’t get it?”

    “You, you…”

    “Rubbing against the vaginal walls with a condom versus bare skin. The feeling’s completely different, don’t you think?”

    “…Ah, there—don’t press while talking…, ah…”

    “Personally… I like this way a lot more.”

    “Hngk…”

    “Watching your ass jiggle while I pound you raw—the sense of conquest is insane.”

    “Fff…, nghhk…”

    I try to glare at him as he slowly thrusts, but it’s no use.

    When I whimper stupidly from the shallow strokes, he drags his cock along my walls, slow and gentle.

    Just as I start to regain my composure, he slams his hips against my ass, forcing himself deep to the hilt like he’s determined to wreck me.

    When I gasp, trying to say something, he pins my shoulder down and crushes my cervix with relentless thrusts.

    And when I tremble, trying to hold back the rising climax, he whispers sweetly into my ear again.

    Beneath Seo Woojin, all I can do is mutter broken curses every time his tip pounds against my cervix.

    In place of my clueless sister,

    I, her younger sister,

    am being used as her boyfriend’s personal toy.

    …When you masturbate,

    you don’t use condoms, right?

    “Definitely getting a better reaction this way.”

    “Fff…uck…, pull out…!”

    “What? Pull what out?”

    “What else would I mean…? Your d…ick, obviously…!”

    “When was your last period?”

    “Stop talking nonsense…! Just, pull out……?! Hngk…?”

    When was my last period again?

    How do you calculate safe days?

    Would it be okay if Woojin came inside by accident?

    …What’s the pregnancy risk during safe days again?

    My tangled thoughts

    thud,

    thud,

    squelch—

    are shattered by Woojin’s relentless thrusts, burying himself to the root.

    The overwhelming pleasure leaves no room for thought.

    So even as I beg him to pull out,

    I’m still

    being fucked by his bare cock,

    dripping slick arousal between my thighs.

    “…You fucking psycho…, y-you can’t…, nghh…, do it raw…”

    “Why not? Say it clearly. So I can understand.”

    “If you want a straight answer…, stop fucking me first…!”

    “…Stop fucking. What?”

    “…Ngh, ah…, j-just slow down a little…”

    “…Say it. Fast.”

    “Ass…hole…, ……nghhk…”

    What if I end up pregnant?

    That’s the scariest part.

    But he doesn’t seem to care,

    too lazy to humor my plea to slow down,

    only reducing his pace

    by a fraction

    before slamming into me like he’s ready to fill me with cum.

    …The way his cock twitches whenever he pauses.

    The way his breathing is even heavier than before after cumming over ten times.

    Even if he rams his tip against my cervix now,

    bites my ear, and starts pumping his load inside,

    it wouldn’t be surprising—

    My sweat-drenched back shudders.

    “Jiyeon. …Be honest, you like this more too, right?”

    “Shut… up…”

    “The time between your orgasms is shorter than before…, …you can feel it, can’t you?”

    “Shut the fuck up…”

    I don’t know.

    I don’t know how different bare sex feels.

    I don’t know if this feels much better than before.

    I don’t understand Woojin’s smug voice telling me I’m cumming faster.

    The only thing that’s changed is my mindset.

    The fear that if Woojin slips up,

    if luck turns against me,

    I could get pregnant.

    And the fact that I’ve experienced raw sex way before my sister, his girlfriend…

    That I might even get pregnant…

    …That…

    …filthy sense of betrayal.

    But you can’t slaughter the goose that lays the golden eggs just for that, can you?

    As long as I don’t get pregnant,

    as long as Hayoon doesn’t find out about us,

    as long as we clean up and keep our mouths shut—

    Like this.

    While our innocent Hayoon cooks stew at home, oblivious.

    I can have affair sex with Woojin in his place until he’s satisfied.

    So I bite my lip, push the latter thought away, and reach back to stop him.

    …But,

    of course.

    “You were holding back earlier, but now you’re cumming almost every thrust.”

    “…N-not that much…, stop exaggerating…”

    “Every. Thrust.”

    “…?! …??! Li…, liar……”

    “You’re cumming. …So hard you’re slurring.”

    “…Hngk……? Hah…?”

    My resistance was useless.

    “…Ah. Fuck… Your reactions are so hot…”

    “Fuck… off…, ngh…, ahh…”

    “Tch…, …nghhk……”

    Useless.

    Completely useless.

    Unless I were as strong as Hayoon, a girl who stays home gaming could never push back against those solid muscles.

    Instead,

    he fucks me harder, turned on by my weak resistance,

    forcing my head back to kiss me.

    So I grip the bedsheet, trying not to let Woojin hear me climax, panting into his mouth.

    As I gasp, his saliva drips into my mouth, and I gulp it down, mixing it with my own.

    …Well.

    Honestly,

    whether I resist roughly

    or submit quietly,

    he doesn’t seem to have any intention of pulling out.

    But if I had to choose,

    this is more my style.

    “…Hah… I’ll pull out to cum, okay?”

    “Fff…, then just use a condom…! What’s the difference? Cumming outside or inside a condom…”

    “Bare feels way better. …Admit it, you prefer this too.”

    “…Not… much…, nghh…, difference…”

    Even now, I don’t get it.

    The only thing that’s changed is my mindset.

    That raw sex feels better or whatever…

    ….

    …Dunno.

    Really.

    Feels the same to me.

    I know my body best.

    “You’ve been cumming every time I slam into you, what do you mean ‘not much difference’?”

    “No…! J-just…, put a condom back on… It’s not like that was the last one, right? I’ll unwrap it. Hurry…”

    “Let’s just keep going. Okay? You’ve been squeezing so tight the condom kept slipping off. Jiyeon.”

    “I’ll… relax…, …huh……?”

    Not even sure how to relax, but determined to avoid the worst, I fumble for the condom wrapper.

    Woojin sighs above me,

    snatches the wrapper from my hand,

    and tosses it far across the bed where I can’t reach it.

    Clatter.

    Swiish.

    The sound of the discarded wrapper skidding across the floor is drowned out

    by his bare cock, slick with precum and my arousal, ruthlessly pounding my cervix.

    “Fff…ucking psycho……. Put on a condom…, nghhk…”

    “…Rather than interrupting the flow to put one on, isn’t pulling out to cum better?”

    “What if…, ngh…, you slip up and cum inside…”

    “Won’t happen.”

    “Like hell…, hngk……. Y-you…”

    The Woojin I first met in the nurse’s office was kind.

    The Woojin who came to find me at the café for my sister’s sake was kind.

    The Woojin who asked me about my sister to impress her was kind.

    Even when the three of us—Hayoon, Woojin, and I—went shopping together, it was the same.

    But Woojin, soaked in lust, is different.

    Playful, a little selfish—not kind.

    …He wasn’t like this yesterday when I overheard him fucking Hayoon.

    Seeing his true face before my sister does

    makes a filthy sense of superiority itch at my heart.

    Don’t you want to see more of my honest self?

    Don’t you want to care about me—your girlfriend’s sister—more than her?

    Don’t you want to prioritize me over some trivial date with my sister?

    Then there’s only one way.

    …The only way

    that comes to mind.

    “…Hah, if I’d known it’d feel this good, I would’ve gone bare sooner.”

    “…Hey. Woo…jin.”

    Woojin, buried to the hilt, whispers filthy things in my ear.

    I grab his arm braced beside me and speak carefully.

    “Yeah?”

    “…You’ll really pull out to cum?”

    “…”

    Permission.

    Permission to go bare.

    With one condition—that he cums outside.

    Hearing this, Woojin exhales softly against my ear, grips my ass, and presses closer.

    “…Is it because you’re in a risky period?”

    “…”

    Even after mustering the courage to allow it,

    he shamelessly wants more.

    …To cum inside.

    He rubs his tip against my cervix

    and murmurs:

    “Why so quiet? …Too shy to say?”

    “…Why… are you even asking…?”

    “Curious.”

    “Bull…shit, you just…, nghh…, wanna cum inside…!”

    “…If it’s a safe day, it shouldn’t matter anyway.”

    “It does…! There’s no guarantee I won’t…, nghhk……, get pregnant…”

    “And you’d… rather have it drip down your back than take it inside?”

    “Shut up, you psycho…, …hngk?! No, no, no…, don’t speed up…”

    I try to reason with him, but it’s pointless.

    Instead,

    thud,

    thud,

    he fucks me like he’s determined to cum inside,

    destroying my mind with pleasure until I’m dumb with it.

    “So, can I cum inside? …Or not?”

    “No…, absolutely not…”

    No.

    I answer clearly, but

    his cock, dragging along my walls before slamming deep, doesn’t change.

    As if to force me to say “yes,”

    he drowns me in pleasure,

    never letting me surface.

    Burying me in that mud,

    never letting me escape.

    Persistent. Relentless.

    “You’re in a safe period, right? Or not?”

    “Stop talking nonsense and pull out…!”

    A flinch—just for a moment.

    Before he notices, I glare at him with dazed eyes.

    Ha. That cheap trick won’t work.

    Do you even know my cycle?

    Guessing like that…

    What if I lied and said I’m in a risky period all 30 days of the month?

    You idiot…

    “If it were a risky period, you wouldn’t have asked earlier, or said safe days aren’t 100% safe. You’d have just said it’s risky.”

    “…Wild…, nghhk…, guess…”

    “So we’re having raw sex on a risky day?”

    “……”

    The only lie is “risky day.”

    But if I agree, I’ll be labeled a pervert for allowing raw sex on a risky day.

    I search for an escape, but pleasure clouds my mind.

    I can only hug the pillow, silent.

    “And you’re the one who allowed it. …Knowing what could happen.”

    “I didn’t…! I kept telling you to use a condom…!”

    “Idiot. If you’d said it’s a risky day, I would’ve used one.”

    “…”

    “What’s the problem with going bare? What was your answer earlier?”

    “…”

    “…Not a word about it being risky. Remember? Jiyeon.”

    “…”

    “All you said was the basics—’use a condom.’ Like some elementary school sex ed.”

    “…”

    “…You’re a pervert, Jiyeon.”

    “…”

    His cock, buried deep, twitches inside me.

    Every word Woojin whispers

    is a plea to cum inside.

    Even without thrusting, small climaxes keep coming.

    Squelch, squelch.

    When Woojin lifts me gently, just that much

    makes me shudder with pleasure for minutes.

    My body’s too sensitive.

    “…Jiyeon.”

    “Hah, hngk…”

    “Are you… in a risky period today?”

    “…”

    The same question, whispered sweetly.

    But his cock tells a different story.

    Even if I can’t yet tell the difference between condom and bare,

    …how hard he is

    is obvious.

    He’s never been this hard except when we fucked over Discord.

    ….

    …Ah.

    Now that I think about it,

    it feels even bigger

    than back then.

    “…Safe day.”

    “…Yeah?”

    Hearing my answer, Woojin exhales and shifts.

    No longer bracing on his arms.

    Too far to kiss, but

    his hips press close,

    burying himself to the hilt.

    …Ready to cum inside.

    “…Then it’s okay if I cum inside?”

    “…Do whatever…, asshole…”

    “…”

    “…You’ve already cum so much, I won’t get pregnant anyway…”

    “…”

    “What? …Getting cold feet now?”

    Woojin, hearing my snark,

    pulls out briefly

    before tossing something

    beside my face.

    “…”

    …A condom.

    Soaked and glistening.

    Dripping with precum.

    Before I can ask,

    Woojin

    “……?!? …? ………♡”

    slams his bare cock

    deep inside me.

    How hot it is.

    How hard.

    How the veins pulse.

    How turned on he is.

    I feel it all—

    his real, bare cock.

    “…Hah… Fuck…”

    “…Hah…? Hngk…?”

    “…Rubber versus bare skin. Feel the difference now?”

    “Ngh……, hah…? Nghh, ah…?”

    “…I can definitely tell now.”

    “Hah…, ah……”

    It’s different.

    The cock wrecking me earlier wasn’t this hot.

    Not this hard.

    Not this throbbing.

    Not this obviously aroused.

    …The condom sex

    felt like mere “practice”

    compared to this.

    “Which do you prefer?”

    “…Dunno…, you bastard…”

    “Don’t curse. Choose.”

    “Choose what…! Fff…”

    “If you prefer condoms, I’ll grab the one I tossed…”

    “Bare…, bare’s way…, nghh…, better…, …happy now…?”

    Even shallow thrusts feel different.

    The way he grinds deep inside is different.

    Woojin fucks me like an animal,

    leaving me panting, biting my lip.

    My back arches,

    toes curling uncontrollably.

    Can I really stay conscious through this?

    It’s barely been 30 seconds, and my vision’s blurring.

    White, black.

    …Can’t even tell colors apart now.

    Hehe.

    “…Hah, you fucking psycho…, just one condom off and you’re squeezing even tighter…”

    “Dunno…, hah…, haa…. G-gimme a break…”

    “It’s barely been a minute. What break?”

    “Break every minute…, my head’s… messed up…”

    “Fucking you stupid is the point. Why would I stop?”

    “Fff…, just cum…, I’m seriously…, seeing white…”

    Maybe mentioning a break was a mistake.

    Or telling him to cum fast.

    His thrusts, already brutal, grow even rougher.

    Pinning my hips down, he fucks me relentlessly,

    twisting his cock inside me like he’s rearranging my guts.

    When he starts thrusting again, he yanks my hair back, forcing me to look up.

    Then, slam, slam.

    He batters the space meant to hold his cum.

    I’m not a toy, you know.

    What if I break?

    …Oh,

    right.

    You’d fix me.

    “……, …? ……♡ ………….”

    Anyway,

    let go of my hair.

    It’s not like you can kiss me from there. Why pull?

    Don’t like me hiding in the pillow?

    …Or do you just want to hear me moan like a bitch?

    Judging by how turned on you got yesterday hearing my sister call you “oppa”…

    Guess that’s your thing.

    “…Jiyeon.”

    “Hah, hngk…”

    “…Really gonna cum inside…, hah…, okay?”

    “Ngh…, nghhk……”

    Well, I can humor you.

    It’s no different from my sister calling you “oppa”

    or imitating a puppy.

    Just this once, as a special service.

    “…Woof…, hehe……”

    “…”

    For a delighted Woojin, I playfully bark.

    I’d wag my ass too, but he’s fucking me too hard.

    Instead, as his grip loosens, I glance back and smirk.

    I don’t smile often, but I know how.

    Keep that in mind.

    I’m really not the type to smile.

    …But I do for you sometimes.

    Guess it doesn’t matter?

    …Whatever.

    Keep it if you want.

    Hehe.

    “…The hell

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