Chapter Text
Olivia grumbles as the sound of her alarm blares inside of her room. Just two more weeks of summer vacation to enjoy before she has to go back to school again, and unlike last summer's end she'll be coming back looking a whole lot different. The 6'4ft tall 13 year old attempts to prop her large overweight and thick body up with her arms as she then goes to wipe the sleep out of her eyes.
When Olivia was born she was diagnosed with a disorder known as "Hyper Growth Genetic Disorder." This disorder lingers dormant within the body until puberty where the symptoms manifest physically; growth spurts that don't stop until the host turns 30 years of age or so. HGGD also only effects futanaris, who in themselves are a small group only making 1% of the human population. There are a total of 14 alive cases of HGGD individuals, and Olivia is one of them. Fully grown people with HGGD usually live in isolation away from the masses, as the tallest known person with HGGD overcasts her shadow onto skyscrapers being 500 feet tall.
Before Olivia gets up from her bed she takes notice of the pest that greets her as she wakes up; her giant 16 inch olive tinted dick that matches the rest of her skin. Groaning she places her hands on her cock to massage it's veiny but smooth and youthful surface as her apple sized balls churn semen. "I already made you cum 6 times last night bitch, why can't you just let me have a normal morning..." The girl mutters to herself in annoyance.
Suddenly Olivia was interrupted by a knock on the door, and a familiar voice. "Sis your breakfast is ready! Get out of bed right this second before it gets cold!".
Olivia would sigh as she stops jerking her giant dick with her own rather large but soft hands. Getting up from her bed the large girl would walk with heavy footsteps over towards her closet which contained a shrinking selection of clothes she could wear. Ever since she started her 'spurts' as her mother cutely calls them the girl has been growing out of house and home with clothes and eating her family out of house and home as well.
The bedhead messy black haired girl goes inside the closet to take cover her rather chubby naked body with some pajamas that are too tight on her; she got them back when she only measured at 5'8ft tall and now they ring up at her calves and forearms. Her dick obscenely gets tucked to the side but bulged as if she had stuck an eggplant within her pants.
Finally after some moment to change Olivia walked out of her room to meet up with her sister who patiently waited for her standing next to the giant pile of breakfast on a large plate that sits on the kitchen table. Olivia's sister Kelsey is younger than Olivia at 10 years old, but despite her age two giant breasts twice the size of Olivia's own head hang inside of Kelsey's oversized bra under her shirt and apron. "What took you so long miss bed head? Mom went off to the office today so I figured I'd make you some breakfast."
Kelsey's eyes trail towards the giant crotch bulge that snakes across Olivia's thigh like an anaconda for a second as she blushes and seems a bit concerned. "That thing just gets bigger and bigger doesn't it?"
Olivia groans and waves away her sister's concerns as she walks her heavy body over towards a chair to sit and begin eating. "Don't worry about it, it's just my burden is all." With having said that Olivia takes her fork and begins eating her large meal made for 3 normal people as she takes bites out of french toast and eggs then sausage.
Smirking at her sister she goes over towards the older sibling and places her hand on her sister's back and watches in amazement as her sister chows down the entire meal. "I bet not only the girls at schools are gonna be chasing after you, but the teachers too~" She teases as she giggles.
Rolling her eyes while continuing to eat, the large girl's dick begins to tent her pajamas as it continues to get harder and stronger from her busty sister's teasing. Olivia's gaze trails towards her sister's enormous rack which causes Kelsey to bite her lower lip and smirk devilishly.
"What's wrong? You like the look of my giant soft boobies?" Kelsey teases her hung big sister as she bunches her tits together with her shoulders; creating a large crease in her apron and shirt as she smiles and shakes her body from side to side to make her breasts jiggle.
Grunting in frustration and blushing like mad as her eyes widen from the sight of her incredibly attractive little sister doing such a thing, the hung teen shakes her head. "Knock it OFF Kelsey!" The older girl demands as she feels her dick continue to get harder and harder, creating rips and tears along her pajama pant leg as her dick wants to force itself free to fuck for the very first time~.
Kelsey takes hold of the bottom of her top and drags the shirt and apron over her head then throwing the pieces of clothing towards the corner. There, before Olivia's gaze, is her sister's giant tits only contained within the large black brazier that hold them in place. "I bet you reaaallly wanna touch em huh? Y'know, I wouldn't mind giving my little sister a few blowjobs and titjobs for some allowance money." The younger preteen bribes.
Before Olivia could respond to that though, a familiar sensation was beginning to ignite within her body. Her eyes once again go wide, not in lustfilled surprise but in partial shock. The tingly numbness begins to creep all along her body as her body temperature begins to accelerate. Sweat droplets begin pouring down her hot tan body as Olivia starts to have some difficulty breathing. . . One of her spurts is about to occur and she knew it.
Suddenly before Kelsey's eyes her sister starts to gain inches in height as her clothes which were already tight begin to tear in multiple areas of the body, revealing her soft light brown sweaty flesh. The smell of intense musk fills the air as the sound of stretching flesh emits from Olivia's body. Olivia's already hard dick tears apart at the weak fabric of her pajamas until the brown veiny dick slams hard against the underside of the table as Olivia shivers in pleasure from the feeling of growing.
Finally the growth stops, and Olivia becomes aware of her surroundings completely again. Olivia is sitting on the kitchen chair, half naked and only wearing torn garments that used to be pajamas. Giving out a frustrated sigh after examining her new condition, she stands up from the table as her musky dick waves in the air. Both Kelsey and Olivia take note of the fact they expected; Olivia was for sure a bit taller.
Kelsey would attempt to appease her big sister by approaching and patting her sister on her soft back. "Awe don't be so glum, I love how big your body gets big sis."
Olivia shakes her head as she doesn't seem the least bit at ease from any of this. From how tall she's standing she could guess she's atleast passed 6'8ft now, and her dick seems to have also grown with her. "Well, if I keep this up I won't be able to even live in this house anymore Kelsey. I'll get so big that I'll have to be the freak giant that lives outside of the city. You know how big the largest person with HGGD is? She's over 200 feet."
Kelsey gives a nod of reassurance but her spirit doesn't submit to Olivia's concerns, she gives her sister a knowing look and replies. "Even if you do get that big, it won't be for a while, and there's an international support network for people like you. That same giant woman lives in a huge luxury house in Montana because of them silly. Though if you do get that big you'll have to watch your step because I plan on living with you, and I don't wanna get stepped on." The busty preteen chuckles as her gaze trails down towards Olivia's giant exposed monster cock. "What a tasty dick~" Kelsey's soft hand goes to softly press itself against the underside of her big sister's dick.
Olivia tenses up but seems to not be retracting herself away from her little sister's advances. "Kelsey you shouldn't , you know mom doesn't want you helping me with it, and besides I don't have allowance till next week.."
Smirking up at her large sister Kelsey would respond. "Well what she won't know won't hurt her anyways and besides; we'll consider this a freebee since you went through another spurt~" Kelsey's other hand grasps at Olivia's giant cock and slowly the oppai little sister's soft hands continue to stroke at her big sister's giant dick as pre shoots out the tip occasionally.
Wincing with pleasure but also from a part of her fighting to not get in trouble, Olivia finally buckles under the pleasurable strokes of her little sister as she moans and both her eyes twitch. "O-okay, but lets do this in my room, I don't wanna make a mess in here and if I do make a mess in my room I'll just say I masterbated.." The large girl concedes defeat as she takes her large hand and gropes her little sister's giant tit.
Caught off guard, Kelsey would blink as her giant soft bronze tit under her bra gets squeezed, but then eventually her surprise turns into erotic fueled excitement as she licks her lips and smirks devilishly up at her big sister. "Alright what you waiting for, c'mon~"
Kelsey takes Olivia by the hand and pull leads her big sister through the house , out of the kitchen and into Olivia's bedroom as Olivia closes the door behind both of them. Suddenly, once the door seals, Olivia squats in front of her sister to kiss her deeply as her own dick starts to rub up against Kelsey's busty body. The wet hot kiss lasted for many moments as Olivia invades Kelsey's mouth with her own tongue. Kelsey started once again stroking the giant mammoth cock of her sister's while they kissed, sucking on Olivia's tongue she moans in pleasure.
Finally the kiss broke as Kelsey asks her sister curiously but with lust motivating her. "So, you got the nuts to actually fuck your sister or do you just want a handjob from me?" The boss bitch little sister smirks at Olivia with a devilishly naughty look in her eyes.
Olivia huffs at being teased so aggressively by her sister "Kelsey! You know we can't , I could get you pregnant and then mom will find out!" She proclaims in defiance to her sister's wishes, but her dick pulsates violently as it wags up and down with every throbbing beat.
Kelsey would take notice of Olivia's overactive dick getting excited at the idea she proposes. "Seems your monster cock is telling me a different thing~" The wickedly horny girl giggles. "And besides sis, remember that international help agency for people with HGGD? They help support the mothers who had been bred by daddies like you who have HGGD~"
Olivia is suddenly surprised and shocked by what she just heard. "Daddy?~" Olivia's dick lurches with excitement again once the large girl heard that.
The large breasted little sister goes to press her beautiful and cute face against the underside of her big sister's giant dick as she peeks from over the side of the monster shaft's girth. "That's you~ You're my daddy big sister as long as we're together alone~" Suddenly Olivia's dick gets peppered with several soft tender kisses from Kelsey's maw as she kisses the cock up and down the shaft while Olivia moans.
Olivia's hand goes to grasp at the underside of Kelsey's head to press her little sister against her cock to not allow her to stop. Pre continues to shoot in thick wads against the wall Olivia's facing as her eyes twitch from such treatment.
Unhooking her bra, Kelsey lets her giant tits twice the size of Olivia's head bounce free in perfect young shape as the soft tits get wrapped around Olivia's shaft slowly~
The sensation of feeling her little sister's titanic sized tits around her own vainy monster cock put the large chubby futanari over the edge as her blubbery but powerful hips thrust against her little sister's movements. Up and down her little sister continued to send shockwaves of pleasure down Olivia's spine as the soft breasts smooched together around the shaft.
Suddenly, Olivia grunted and huffed as she took hold of her sister's breasts and began to accelerate the pace. The strength of her bigger sister caused every motion to shake Kelsey's body as Olivia went closer and closer to orgasm. Olivia's dick throbs violently as she shoots her powerful load all over her sister's body while she moans and pants in sexual heat. Every long thick rope lands on Kelsey making her smell of her bigger sister's seed as the young girl twitches in pleasure, having an orgasm herself from the rough treatment she received on her sensitive tits.
Once Olivia's orgasm subsided, her dick remained rock hard as it spit out it's last drops of cum. Having taken note of that Olivia takes hold of Kelsey and brings her up to hang over her own shoulder as she carries her little sister towards her own bed. Kelsey gets let go as she falls down towards the mattress below and suddenly her big sister's dick gets pressed against the loli's body. It's musky stench and heat radiate off the cock flesh and invades Kelsey's senses, making the little girl drunk on her big sister's hazy musk.
Olivia steps back a bit and spreads her little sister's legs as she takes off her little sister's pants; damned if she gets introuble and damned if she gets her little sister pregnant, she just wants to cum over and over again inside her sister's pussy. Once her bottoms were removed and Kelsey's wet thick pussy became exposed, Olivia places her giant hard dick head against her sister's pussy and begins to thrust to part Kelsey's pussy lips.
Kelsey's eyes go wide as her pussy begins to open up and stretch around her big sister's cock, moaning and almost screaming with how high her voice is getting from this experience, her eyes twitch as she gets used by her little sister like a sex toy. Both of Olivia's large hands rest against Kelsey's thick waist as she pushes her thrusts to get her own cock nice and deep into her little sister's body. Over and over the cock gets deeper and with each thrust Kelsey's body gets pushed farther by the thick veiny shaft that continues to slide in.
Once Olivia felt her balls start to slap against Olivia's ass, she looks down to see her huge monster dick bulging from Kelsey's stomach as she moans and continues to thrust her pelvis into her sister's sexually overdeveloped body. The two were incoherently drunk on lust and pleasure as the two fuck like rabbits on Olivia's bed. They switched positions numerous ways, and with each positions Olivia's dick gave Kelsey a powerful orgasm that shook her body to the core with unbelievable pleasure.
Kelsey felt Olivia's giant bitch breaker throb inside her as she huffs in pleasure, sweating equal to how much Olivia is as they drench eachother in their sexually charged sweat and musk. Finally, Olivia's dick busted the fattest nut it had ever given, as the dick erupts it's orgasm through Kelsey's body. There was so much cum inside of Kelsey that it looked like she was pregnant for 6 months with twins, and it wasn't over as blast after blast of white baby batter hit Kelsey's G spot causing the little girl to reach her own orgasm. . .
. . . Eventually the two would rest in Olivia's cum drenched bed after a morning of nonstop fucking, Olivia could get used to this and she seemed to not mind sex. In fact, she began to love sex. She couldn't get enough of it, she wanted more and she didn't care the consequences. Kelsey was unconscious atop her body laying asleep, seems like she passed out from everything she endured. Olivia's cock however rose high once more, 16 orgasms hadn't made her needy monster dick tired in the slightest. Olivia picked up her sister and plunged her deep down her cock once more as she used her sister like an unconscious sex doll for a few hours to get her cock asleep, after all, she has special needs that need to be fulfilled and an appetite for sex that won't die down easily.