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vanillakook · 3 months ago

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THE BOY IS MINE ꔫ - JJK

synopsis: your big sister has a new boyfriend that you can’t wait to try

parings: jk x sister in law!reader

warnings: infidelity, reader is a heavy bitch, she doesn’t care at all, strained relationships, traumatic sibling rivalry, dom!jk, fat cock!jk, sneaking around, exhibitionism, voyeurism, penetrative sex, oral sex (m. and f. receiving), fingering, rough fucking, multiple positions, reader’s pussy is an OCEAN, all hyewon does is cry, reader is actually evil, jungkook is just as bad, if not worse

genre: smut, oneshot

word count: 5.4k

nothing could have prepared jungkook for the influx of strange events that would take place over the next month. his time starts as it usually does: hyewon, his girlfriend, freaking the fuck out about every interaction he’s had and will have with her family. however, something was different this time. hyewon’s usual dread of embarrassment had shifted into full blown panic and anxiety. he was utterly confused since she had never been this bad. did something happen? he was sure her parents liked him, no? why would they let them date for nearly a year if that was the case?

jungkook had come to know why on the three hour long drive to her parents lake house. after prying he had found out it was you, her baby sister who is supposedly the devil incarnate. “i’m sure this is just a normal sibling rivalry hye, baby, my brother and i are the same way.”

“jungkook,” she closed her eyes and took a deep breath. “im telling you it’s not the same.”

she excused it when you were kids, but after a certain point of awareness she knew that this wasn’t a silly little rivalry, you hated her. despite you being younger by three years you had always went out of your way to make sure she was miserable. in your childhood years it started out as lying to your parents about her hitting you, or sneaking gum into her hair, breaking her dolls. these little things progressed to stealing her clothes and ruining her makeup products in middle school. once high school came around whatever she did you had to do it ten times better. clothes, shoes, sports, friends, boys. your parents had just seen it as a cute thing between a younger and older sister. little did your parents know that soon your behaviors turned cold with sinister intent, from ruining her friendships, straining her parental relationship, and fucking every single guy she’s ever bought home.

hyewon grew up with the same speech throughout her middle school and teenage years, even now in her 20s.

“she just admires you.”

“you’re her role model.”

“y/n has it all, have you ever thought that you’re the jealous one?”

bullshit.

your parents also weren’t shy about who was the favorite. although the two of you had done nearly every sport and form of hobby together, your awards were hung the highest, your interests were more funded, and you were taken more seriously. they insisted that it was just in her head for so many years, more like they were being heavily manipulated by you. now finally her boyfriend of 11 months was going go meet you in less than an hour to see for himself how fucked up you were.

the boyfriend that she so desperately has tried to keep away for so long. now her time was up.

hyewon was successful with that aspect for a while since you were dorming hours away at college. she successfully avoided holidays, family dinners, special occasions, all for almost a year. while she did limit how much she posted jungkook, she was never too sure with the extent you would go with things and has kept you blocked and hidden from all things him.

she could have avoided it for longer if this hadn’t been your first summer back from school in years and your parents were adamant on having the entire family together. usually you were able to make an excuse on why jungkook couldn’t come, work, family matters, etc. but everyone was to be at your family lake house for a full month, and that included jungkook.

“hye ill be there, all month. you have nothing to worry about.” he gave her thigh a soft squeeze and flashed his reassuring bunny smile.

“promise?”

“promise.”

jungkook couldn’t be more unaware about what exactly he was promising to. and as he rounded the corner and pulled into the hidden entrance and drove down the dirt road, hyewon grew more anxious and clammy. she felt her heart sink deeper as jungkook pulled into the driveway and parked. once she saw your sunglasses go up she knew she was fucked. skin tight red bikini, slurping on a melting strawberry popsicle, with her boyfriend ogling every curve of your body. she could have shot herself right there.

over the next month hyewon would watch her perfect relationship crumble to dust. if you were going to be trapped here all summer with your insufferable sister the least she could do was share her boyfriend. her first mistake was pulling you aside that night before bed for a talk. you followed her out to the patio and faced her, finally dropping the innocent facade you’re forced to have around others.

“what now hyewon?” you scoffed. “i haven’t seen you in a year and you’re already about to scold me about something?”

you were trying so hard not to laugh at her angry demeanor. “stay away from him. y/n i understand you can’t keep a man but that doesn’t mean you can help yourself to mine.“

you pouted at her, prying her folded arms open and taking her hands in yours. “but hyewonniee~ that’s not fair, we share everything, what would mommy and daddy say to you right now?” you tsked obnoxiously.

she snatched her hands away. “y/n, this isn’t the time to play your sick games. what the fuck don’t you get? i’m not asking you, im fucking telling your twisted ass to leave us alone.”

“come on sis live a little, i promise ill give him back,” she felt like she was going to throw up right into the lake beside you two.

“please y/n…” her voice cracked.

all you could do was give her that fuck ass smile as if you were clueless about every goddamn thing in the world. “i just wanna try him, no need to get fussy.”

that night at dinner she kept a close eye on you whenever you were near him. she allowed the small talk and conversations about his family and work, but was steadily getting annoyed when no one had been asking a single thing about what she’d been up to, obviously not you, not your parents, and not even jungkook, in fact her very far gone boyfriend was looking at you as if you had hung the stars and the moon with your bare hands. he hadn’t taken his eyes off of you as explained your college stories and travels. your sister on the other hand had her head down in her phone, earning a scowl from your parents and a few words from her own boyfriend.

“hyewon,” your father cleared his throat. “don’t you think it’s poor manners to not listen to what your sister has to say? she listens to you.”

“right, sorry.” she mumbled, putting her phone down to pick at her food.

“apologies jungkook, they’ve been this way since they were young. just a little squabble here and there.” your mother leaned over the table a squeezed his hand, to that he replied with a smile.

do little squabbles consist of fucking someone’s boyfriends and sending them the tapes of them doing so?

“trust me i understand, my older brother and i are sworn enemies but he’s my entire world.”

you decided to chimed in too. “hyewonnie doesn’t ever think i have anything interesting to say,” you pouted. ��actually enough about me, sis how’s your desk job? still letting that old hag of a boss order you around?”

any normal boyfriend would take his girlfriends defense when a backhanded comment was made. instead jungkook, who was seated in between the both of you, pealed his eyes away from you for once and turned to his girlfriend. he was also waiting for her response to that. all eyes were now turned to her. you have her that knowing smirk, a smirk that knew since your lasting meeting a year ago, she had accomplished absolutely nothing but scoring a hot boyfriend. and even that was going to be ripped away from her shortly.

“i’m working on finding a new job.”

“work harder then hyewon, look at your sister.” ah here we go. your father was about to go on his comparison spiel. “y/n is set to graduate early after studying abroad and even has a job lined up for her after school, meanwhile you’ve been stuck at this little start up company for how long?”

“we love you honey, dearly. but it’s time to start being an adult.” your mom had delivered the final blow. hyewon stood up from her seat, fork clinging against the china plate.

“i need to use the restroom.”

no one tried to stop her, instead everyone fell back into a steady stream of conversation. jungkook however couldn’t even bring himself to have another thought other than you. he couldn’t have made his attraction to you more obvious. you were so fucking pretty, he hasn’t seen a being like you. sweet and delicate tone with hints of seduction. he wanted to feel bad for being more attracted to you than he was to your older sister, but fuck. your hair was pulled back into a neat bun and your dress had just reached below your ass. he tried his hardest to not stare for too long, but when you had suddenly dropped your fork and bent over to go get it he was in for quite the treat that couldn’t be passed up.

when you rose from your chair, slick trails followed behind. you hadn’t been wearing underwear and your pussy had been drooling all over the wooden chairs, leaving you with a pool of pussy juice in your seat. your cheeks burned, knowing his eyes were on you and your pretty pussy. he looked between you and your parents, hoping they weren’t seeing your antics so he could bask in it longer. luckily they were immersed in conversation.

“whoopsies, i’m so clumsy sometimes!” you sat down in your seat again, making sure he heard the wet plop! of your ass on the sticky chair. you flashed him flirty smile, once again starting small talk. “so you’re a personal trainer right?”

“mhm i am, you know anything about it?”

“enlighten me.”

“well it’s-“ his face dropped and went bright red at the feeling of your hands on him. your palm had sprawled out on his thigh, inching dangerously close to his hardening cock. “it’s um- it takes a while to um-“

“something the matter?” yes something was the fucking matter. your acrylic covered hand was now covering the growing tent in his pants. his girlfriends baby sister was palming his dick at the dining room table, in front of your fucking parents. “sounds like an easy job, maybe you could train me too, i’m a fast learner, and i haven’t worked out in ages…” your eyes narrowed, tone getting lower and heavier.

“hey we’re going to start cleaning up, you kiddos finished with your food?” your mom started confiscating the plates and dishes as you worked at jungkooks zipper, desperately wanting to get a look at the huge cock you were groping.

“we’re not kids mom, we’re in our early 20s.”

“oh fine fine, when your sister comes back from her mini temper tantrum tell her i put her food in the fridge if she wants to finish it.” once your parents were gone you could finally cut the small talk and get right to the point, except jungkook had halted your actions, removing your hand and holding it in his while you bit back a grin.

“what the fuck is wrong with you? do you know how much this would hurt your sister?”

“so?”

“so? are you out of your mind?”

you rolled your eyes. “oh now you wanna play moral police after you’ve been eye fucking me the entire night and almost came in your pants from my hand alone?” if he really didn’t want it you were going to back off. you pulled away completely and scooted your chair over.

jungkook leaned in closer, pining you against your chair. “you wanna feel up on my dick? go ahead sweetheart, but not at the same fucking table your parents are eating at. hyewon could walk in any second too, you really wanna risk her seeing this? risk her ending this before i get to ruin you?”

oh. oh.

“you wanna ruin me? your girlfriends little sister? you really don’t care about her do you?” your eyes lit up once again.

jungkook looked around, peering around the corners of the house to make sure it was clear before what he did next. lust was fully taken over, any thoughts of hyewon were gone, and it was only a few hours into knowing your little minx ass but he wanted to be consumed by you. his hand went around your neck, gripping it to the point where your circulation was almost severed. “i just wanna try you baby, see if i chose the wrong sister or not. and anyways, whatever hye doesn’t know won’t hurt her right? now c’mere pretty.”

the stars had aligned in that moment for you. you had jungkook right where you wanted him.

however she did. hyewon knew exactly what would happen once she left the table, it was her way of accepting defeat. as hyewon sobbed in the bathroom she knew her sister and boyfriend were exchanging more than holy words and touches. she knew how quick you worked. when it came to ruining everything she loved and desired you were always quick. luckily she couldn’t witness the vile things happening at that dining room table.

“gosh, this fucking pussy,” he landed a slap to your sopping cunt. poor baby was crying down there for some action, clenching that tight hole around nothing and pushing out more and more thick ropes of slick. “damn baby i knew you wanted this dick, but fucking hell.” he couldn’t believe how soaked you were, he knew he’d slip his cock in with ease, nothing like your sister.

“aw kook, you must be so bored with her if you feel this comfortable with playing in my pussy. look at you throwing a year down the drain.” and you couldn’t be happier about it.

“fucking tell me about it. love my baby to death but a man has needs you know?” he took another glance around before unzipping his pants fully this time and placing your hand over his fat cock once again. “hye never knows what to do with it, but i’m sure a slut like you will.”

he tugged his boxers down and you watched his angry member spring up, slapping against his stomach with a mean, red tip that was throbbing for attention. your mouth gaped open at the sight of the pretty thing. lengthy, girthy, veiny, and in need of a tight little pussy gripping around it. “make it quick and i’ll make sure to take good care of you later sweetheart.” he guided you to your knees, sat back, and enjoyed your mouth. all while hyewon sobbed her heart out a few feet away.

later that night after you were coming back from a late night jog, hyewon was ready in the living room for you. she needed to put her foot down for once. every other time was different, but this was her chance to salvage her relationship. once you stepped in the door she stood, to which you didn’t pay her a second glance. “the hell do you want? you’re stalking me now?”

“if you keep trying your luck with jungkook im telling mom and dad.”

you let out a mocking cackle as you made your way to grab a glass of water. “what are we? fucking five? maybe if you knew how to pleasure your boyfriend we wouldn’t be in this situation,”

her mouth went dry. “what?”

“oops… well cats out the bag. when you decided to go be dramatic and cry in the bathroom as if anyone cared, jungkook was very quick to say how much of a bad fuck you were.” you provoked her farther. you were younger, you were shorter, but still you loomed over her, in every aspect, in every way, of every day of your lives. “you always pick the easy ones. the ones who hate you more specifically.”

“jungkook loves me, something you’ll never experience.” she spat.

you grinned, leaning against the counter nonchalantly before breaking her heart in two. “and he’s gonna love this pussy even more. he already loves one of my holes. ask him about it.” you shot her a wink before leaving for bed.

there was still a month to go and as the weeks progressed she watched his eyes linger more as your clothes got tighter. she watched your touches get lower. she watched your hangouts go from the three of you to just you and her boyfriend. she watched how you two would talk for hours then get silent when she entered a room. she watched you press your ass up against him when squeezing around tight spaces. it was only a matter of time before she was phased out completely, but she still wouldn’t go down without a fight. jungkook was the greatest thing to ever happen to her, he was worth fighting for, she felt it, she knew it.

yet obviously he didn’t see her the same. he couldn’t care less about his relationship more than ever now since you had given him the best head of his life. now every night, just like this one, he was nose deep in your cunt, devouring you. jungkook waited until hyewon was sound asleep before he slipped himself into your room in the late hours of the night. thank goodness she picked the ones who were skilled with their tongue, because this was just the stress reliever you needed,

cumming down her boyfriends throat for the third time tonight.

“f-fffuck!” your back arched upwards from the feeling of his tongue dragging down your slit. he simply pushed you back down, using the weight of his hand to keep you there. “too much, ‘s too much koo!” you pulled at his hair roughly, making him groan deliciously. how the fuck did you taste like this? you were becoming his favorite flavor.

“oh yeah too much?” he took two fingers, plunging them inside of your cunt and watching the disappear deeper with every thrust. “so fucking wet for me doll, look at how you’re drenching my fingers.” he kept his voice low while your screams went wild. part of him even hoped your cries awoke your sister. he was so fucked up for wanting this, wanting her to see how good he fucked her pretty little sister. he wanted her to see how he fucked her sister in every way that he would never fuck her. he was sick as hell.

his fingers rammed against your g spot roughly. your mind fogged up, making your words start to come out in nothing but incoherent babbles. your body went limp from the amount of times he had dragged your nut out of you tonight. “c’mon princess, gimme one more, right on my fingers. be a good girl and cum baby, cum.”

“holy shiiiiii- awh fuck fuck, fuck i’m- jungkookk!” you whined with tears streaming down your face. with one more clench of your hole and a few more angry thrusts of his fingers you were soaking your sheets and his face. once jungkook removed his fingers you released everything he was keeping inside. he dove right back into you nose first to catch all of the creamy slick dripping from your hole. you couldn’t handle overstimulation, trying time and time again to get him away from your pussy before you came again.

“stop, stop stop- fucking hell stop!” trying to push him away was useless, you were starting to realize he did this shit for his own pleasure.

once he decided he was finished his meal he pulled back, looking up at your flustered and tear stained face. he smirked to himself when he saw your needy pussy still clenching around nothing. it took time for your body to shake off the after effects of your orgasm, but he stood by and waited for you to come back to earth. “better get back before your sister wakes up, you good mama?” he sucked your essence off of his fingers, making you lick your lips at the action.

“already? one more hour, please?”

“it’s starting to get harder to say no to you.” he laid between your legs, trying his hardest not to accidentally push against your sensitive clit. you admired him from this view, his soft features and the various piercings that graced his lip and ears. he was so goddamn handsome, you felt bad that he had to settle for your basic sister. “what are you thinking?” he chimed.

“nothing much, just about how glad i am hyewon bought you home, it’s like she just knew you were right for me.” fuck, you were twisted.

“you’re going to get me in so much trouble doll, what will your parents think of me if they find out?”

you shrugged. “they could care less. everyone knows she can’t keep a guy.”

“and i’m guessing that’s due to you?” he smirked.

you tried to fight your smile but it was useless. “i wouldn’t say that. it’s just that every guy reconsiders when they see she has a sister.”

that was exactly what was happening here now. jungkooks brain chemistry was being altered to only think of you, to only want you, and the month wasn’t even over yet. the way he had pulled away would be the reason for hyewon’s nagging every night after bed from now on. she garnered argument after argument every night in bed, trying desperately for jungkook to see where this behavior was wrong. he was too far gone by now, getting defensive when hyewon would state the obvious.

“you’re acting fucking crazy!” jungkook fumbled out of the bed angrily, snatching a pillow and extra blanket to take to the couch. “she’s your sister, do you hear yourself?” he yelled, as if you didn’t just have a face full of his cock for dessert under the dining room table two weeks ago, as if he wasn’t knuckles deep in you the night prior. he knew it was wrong, he knew it was disrespectful to do it while staying in the same house as your parents. but fucking hell.

he felt like needed you more after tasting you once. he felt sick for not even being attracted to his girlfriend anymore. he felt disappointed in himself for letting almost a year go down the drain. but you felt better than anything.

“jungkook she’s trying to steal you from me, she’s- do you not see? has she manipulated you that far already?” hyewon was on the verge of tears, lower limp trembling as she stared back at jungkook. he gave her an annoyed look and sighed, getting ready to pull out manipulative tactics of his own.

“i understand you might envy her, she’s younger, she gets along well with your parents, but when you start making shit up out of jealousy it doesn’t look good hye.” what the fuck could you have done to make him so far gone? what the fuck had you been spewing to him?

“do you fucking hear yourself? you’re defending a bitch you’ve known two weeks!” she was losing her mind, truly. “you’ve been so distant kook, you don’t hold me anymore, you barely kiss me, and it all started when we fucking got here! you told me you be on my side for this trip, mine, not hers.” her voice cracked but he still couldn’t find it in him to care.

“until you sort your hissy fit out, i’ll be on the couch.” he shut the door behind him and she could hear shuffling down the steps growing fainter. her head was pounding from all this nonsense. she hadn’t had one normal day since stepping in this lake house. her family was indifferent to her and now another boyfriend of hers was trying to convince her she was crazy. jungkook did a terrible job however, because once she heard your door creak open in the middle of the night, she knew exactly where you were going.

and she followed.

hyewon crept her way down the stairs, careful not to let anyone hear. she could hear jungkook’s raspy voice and your soft giggles, along with a very smacking noises followed after. even though she has witnessed you ruin her relationships time and time again, nothing could prepare her for what she was about to see. when she rounded the corner her heart dropped to the pit of her stomach. there you were, on all fours in front of her boyfriend, with your pants pulled over your ass, and a big, heavy dick fucking you into the pillow cushions. her boyfriend, the love of her life, fucking you into the pillow cushions.

her hand flew over her mouth and she bit back tears, watching you and jungkook fuck her over in plain sight. it was over. everything she worked to salvage, it was gone. yet she couldn’t peel her eyes away from the sight. from seeing how much more intimate he was with you. she flinched when he smacked your ass harshly. she needed to stop this, but why couldn’t she? hyewon was frozen in place, forced to watch jungkook give himself to you.

“shiiiiitt- pussy squeezing me baby, control that cunt so i don’t cum quick.” he pulled out, pumping your slick up and down his shaft. you wiggled your ass around, smacking it against his pelvis in desperation. you needed your cunt filled again. “calm down mama, fuck.”

“can’tttt,” you dragged. “hmph. fuck me or i’ll do it myself.” you should have never said that. jungkook pulled you back by your hair, his hand gripping your jaw and forcing you to look at him. your back arched in a painful way and your pussy was leaking on he cushions.

“spoiled fucking brat, think i’m obligated to fill your holes? don’t get this twisted.” he removed his hand from around his cock to smack your tits around, mesmerized with how the perky mounds looked. “making me cheat on my girlfriend, making me fall in love with this pussy. all this is your fault, now get down and throw that shit back.” without warning he slid in. the stretch was painfully addicting.

“koo! you’re so fucking big- nnnnghhh shiitt,” once you were used to the stretch you started to move back on him, when he saw your hand moving to circle your clit he yanked it back. he held it behind your back to ensure you didn’t make the same mistake again. of course your bratty ass couldn’t resist pissing him off even more and tried again. now both of your arms were folded behind you with half your face being smothered in the couch.

“you know- hmph-“ he started saying in between strokes. “one thing about your sister? she knows how to listen. trained her well. guess you need the same don’t you?” you nodded with a bright smile on your face that would soon be wiped. hyewon sobbed softly around the corner, listening to the way jungkook carelessly spoke about her. “fuck, you’re perfect. i wanna see you baby c’mere.” you were flipped on your back now, switching from one position to the other.

when you didn’t think it could get any better, jungkook dragged your legs up to his broad shoulders and he was now face to face with you. you shook your head no repeatedly, something that just provoked him more. his big brown eyes narrowed as he slammed himself into you. “ohhhhh-“ you were so fucking done for. he hit your soft spot repeatedly, abusing your mushy walls with his heavy cock. you tried keeping your whines to a minimum but once jungkook saw a certain someone lurking he wanted to hear more.

jungkook had looked up and made direct eye contact with hyewon, unfaltering eyes burning holes into her skull. he picked up his pace, slamming his hips into you and knocking the breath out of you every time. what a dumb bitch was all he could think. did she really expect him not to indulge in her minx of a sister? she trusted him to keep his composure while you were walking around in little to no clothes? pathetic. jungkook kept stroking you mainly because he knew hyewon wouldn’t do a fucking thing. she would sit right there and take it, just how you were taking him. “look princess, got a visitor.”

your head whipped around, seeing your sister trembling. if you were normal this would hurt you just as much, betraying her in such a foul manner. however, you hated her. you’ve hated her ever since you figured you weren’t the only child. you had been ruining her life forever to guarantee she would get the hint and leave the family. that was why you started targeting her boyfriends, if she kept getting them taken then naturally she would stay away. but she didn’t, and now here we were again, you wished you could say you hated to do this, but she needed to learn. after this you were going to guarantee she’d be far from not only you and your parents, but jungkook too.

“hyewonnie!” a squeal sounded from you. jungkook slowed his pace down. “god he’s so good, i’m so fucking glad you found him big sis,” your hands went up and stroked his round cheeks, running your acrylics over his skin. “after he fills me up with some babies we’re gonna get married and have a nice big wedding that you’ll never set foot on.”

blow after blow. you knew how to make her hurt.

“baby…” he panted on top of you. he buried his face in the crook of your neck and pressed kisses to the sweet spot before mumbling into your skin. “no need to be so harsh, i think she gets it love.”

“i fucking hate you both. you’re nothing to me, this entire family is nothing to me.” she finally spoke.

“mhmm, right there koo, so fucking deep-“ your eyes rolled back and you tuned her out, focusing only on the sensual way you were being fucked. “want you to cum in me, fill my cunt up baby, make me a mama.” something feral snapped in jungkook. as his speed picked up his kisses became rougher, biting up and down your shoulders and your neck to mark you. hyewon watched as you two shared such an intimate moment, hating herself for wishing she was you.

“cum with me doll.” that was all it took for you to release all over his cock. plop! plop! plop! was all that could be heard once he emptied his balls inside of you. jungkook struggled to catch his breath. once he pulled out you both watched the waterfall of cum drip from your fucked out hole. he took his cock in his hand and with the tip, pushed it all back inside. “can’t let that get away now can we?”

that had sent hyewon over the edge truly. she stomped up the stairs and barged into her room, starting to repack her suitcase early. yet she was trapped. jungkook was her ride here. she could ask your parents but it was such a long drive back to where she lived. she was stuck here with the both of you for two more weeks. how was she supposed to explain this to her friends, her co workers, everyone who thought jungkook would be her final. this was the icing on the cake that made her despise you. any love she had was far gone now. she sobbed and sobbed while listening to yours and jungkooks shared giggles, hearing him run you a shower and talk the night away.

once jungkook was asleep in your bed, you stood in her door way, basking at how much of a wreck she was. she didn’t need to look up to feel your presence. “what now? what y/n? you’ve done enough and after this consider me gone from all of your lives.”

“you’re so dramatic oh god. you’re acting like i didn’t warn you.” you welcomed yourself into her room. “think i might keep him around, i actually like him. thank you sis.” your hands went over your heart.

she backed up farther onto her bed. “stay away from me you evil fuck.”

“hyewonnie, i told you from the moment i saw him, the boy is mine.”

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