Her sister, Felicity

Bianca **** herself to continue walking away from the enthusiastic and **** sounds of her transformed friend repeatedly masturbating and sucking herself off to completion. She would have loved to join her, but she was hungry for someone else. Specifically, her older sister, Felicity.

The recently transformed futa quickly made her way through the bunker, though not out of a desire to stay hidden. Honestly, she couldn't care less if someone found her. She knew that with a quick taste of her cock, they'd quickly join her in hopeless, horny depravity. No, she just wanted to get to her sister before she couldn't stand the pressure in her balls anymore and crumbled to the temptation to jerk herself off. Her first load wasn't going to go anywhere but inside her sibling's cunt.

Within two minutes, Bianca was locking the door to her and Felicity's room, eyes fixated on the twenty-six year old laying on her bed, reading. Bianca had always been jealous of her sister's slimmer figure, but now the statuesque futa could only see imperfect flesh that could be made beautiful, in particularly with the addition of a cock, both grown from her crotch and shoved up her cunt.

Felicity only noticed her presence when she felt the edge of the bed sink under her weight. She was in the middle of turning when Bianca grabbed her shirt and roughly tore the flimsy garment off of her, exposing her bra-less tits.

"Aww, look at you, big sis. Not so big anymore. Nice ass though, don't mind if I help myself." Bianca giggled madly as she pulled her sister's loose sweatpants off of her, taking her panties with them, leaving the older girl entirely naked.

"What-Bianca! What happened to you?" Felicity asked, catching a glimpse of her new sister before she was grabbed by her loose, similarly white hair and **** back down on the bed. Bianca wasted no time wedging her leaking cock between her ass cheeks, seeking out her tight pussy with her new appendage, eager to relieve the restrained lust she was holding back as best she could.

"Don't worry about it. You'll be the same soon enough. Until then, I'm gonna use your cunt until you're begging me for more. Sounds fun, right?"

"No, it do-aaahhh!" Bianca had found her sister's slit and immediately pushed inside, penetrating and stretching the older girl without warning. Felicity winced at the feeling, but the pain she had expected never came. Instead, dangerous pleasure coursed through her, her body already feeling the effects of the virus.

"This was-*ngh*-a good-*anh*-choice. Your-*mmh*-cunt is the...oh, oh, OH FUCK YES, I'M CUMMING. YOU'RE THE BEST SIS!!" Bianca's amateur thrusts and broken dirty talk were both halted by the sudden onset of her first orgasm with her cock, the thick semen her body was churning out spilling into her older sister's tight, grasping pussy. Fully seated in the older girl, the virus went to work, perfecting and amplifying her body.

"Bianca, why? I'm hot, so hot. My boobs, why are my boobs growing? What have you done-aagnh~!" The older sibling's questions were stopped by the thickening of her legs and the concentration of feeling at her crotch.

"I love you sis, I want you to be a hot, slutty, fuckable dick girl just like me," she said, grabbing her sister by the head and arm and twisting her so she could see her face better. "Oh, I know that look. Your cock is coming in, isn't it? Your tits are so pretty too, I can't wait to see them bounce when you return the favor." Without warning, she came again, more fresh jizz filling the older of the sisters.

"What are you ta-*nngahhh*-talking about?"

"For when you fuck me. I shared with you, so I get to have you cum inside me too. Oooo, maybe we can get each other pregnant. I'd love to see you give birth to our own futa daughter. So grow that cock nice and big so she can have a slutty sister of her own." Bianca's encouragement was too much for Felicity, and the transforming woman finally came, a slow but powerful orgasm that coursed through her body as her changes finished.

Felicity's cock, small and flaccid, immediately gained another few inches as it throbbed and rose to attention, jabbing at the air in time with her heartbeat. Her ass finished pushing out, the full round orbs pressing back into her sister's abdomen with each of the other girl's thrusts, triggering ripples in her thighs as well. Her tits, not much bigger than their original C's, stretched as the fatty mounds rapidly expanded, her pink nipples standing out sharply at their peaks. Through it all, waves of bliss and tantalizing pleasure ran through her, the virus embedding the desire for sex deep in her flesh.

Feeling Felicity's even tighter pussy release its **** grip on her still-erect cock, Bianca slowly eased out, reveling in the small wave of cum that followed the head of her dick out. Felicity was breathing heavily and trying to regain her senses, a feeling Bianca was well familiar with from her own transformation not ten minutes prior. Even more, she knew the mad desires that were pressing at her sister's mind, the new instinct to fuck, cum, and breed crushing most other thoughts. Eager to help, she rolled over and presented her with her wiggling ass.

"Now come on sis, put that shiny new shaft to good use. I gave you my first, so you should do the same. Plug my pussy with that big dick and let me milk you!" Bianca watched as her older sister came back to herself, her blissed out eyes immediately landing on sibling's perfect butt and dripping cunt. Burning conflict tore at her, part of her horrified at the thought of fucking her sister. But another new and much larger part of herself, namely her girthy cock, positively begged her to put it to good use.