A bit of sibling jealousy results in an unexpected gift

'Matching outfit day with Lina! Well, almost~ ;)'

Lina huffed in annoyance when she saw the picture her sister, Theresa, had posted online that day. Her older sibling never ceased to rub in in her face that she was the sexier of them, with a prettier face, better makeup, nicer hair, and, most importantly, bigger tits. She should have known the bitch was up to something when she suggested they wear matching clothes, but, maybe out of some misguided hope of sisterly affection, had worn them anyways. Nice to see that Theresa thought being a sister meant throwing her under the bus.

'Or maybe under the bust would be a better term,' she thought looking at Theresa's bulging tits in the picture, comparing them to her own, both on camera and in reality. The scooped neck of her shirt only showed off how vastly lesser she was in the chest department. Smaller breasts, more sag, worse skin. No one would go for her when they could go for Theresa, and she wouldn't blame them.

Feeling suitably miserable with herself, Lina sighed and put down her phone, fighting against her urge to look at the comments confirming what she already knew. Pushing the thoughts away as much as possible, she went back to what she had been doing before the notification of Theresa's post came through: gardening. Something she was objectively better at than her sister, who killed every plant she tried to care for.

Not that either of them had to. Every flower and bush on her parents' estate was cared for by their hired gardener, who came by twice a week to make sure everything was still in perfect condition. It was actually thanks to him that Lina discovered her love of gardening. She had been watching him take care of a seedbed one day and asked if she could help. It had only taken a few minutes of **** to get him to agree and she had immediately been in love. Convincing her 'the-world-itself-isn't-good-enough-for-our-little-girls-(mainly-Theresa)' parents, to let her spend her free time digging in the dirt had taken a little more work, but their spoiling nature had ultimately won out.

Humming happily with her arms up to her elbows covered in potting soil, Lina continued to work on her little corner of the garden when she noticed a new plant. She didn't remember planting it and knew the gardener wouldn't have touched her soil patch. It was far too big to have just sprouted too, the stem already bearing a red, teardrop shaped flower that hung heavily from the plant. More than curious, Lina reached over to examine the odd flower, not recognizing it as one she knew.

"What are you, little guy?" she asked, gently moving the closed bulb to look closer at it. Slowly so as not to hurt it, she examined every inch of the odd plant, but couldn't identify anything that she could use to figure out what it was. It did smell good though, she thought, leaning closer to catch another whiff. The smell reminded her of the warm heat of being beneath blankets, tender embraces, stolen kisses, and, though she was embarrassed to admit it, heated sex. Though how she knew that didn't make much sense, thanks to her decidedly still being a virgin. Either way, she knew that was the smell and couldn't help but shiver a little with desire.

She took one last deep sniff, resolving that she would do some research to figure out what the plant was after, but moved just a little too close. The flower, an extension of the massive wall that surrounded the city and just as infectious, squirted the load of viral liquid it had been building up right into Lina's face.

The surprised girl immediately fell backwards, sputtering with shock and trying to wipe the sticky stuff out of her eyes. Much of the clear liquid dripped down onto her chest, still exposed by the low cut shirt she hadn't bothered to change out of. Unseen, the plant shriveled away and disappeared, its job finished and its existence forgotten as Lina tried to get its messy juices off, not knowing the damage was already done.

Resigning that she couldn't get the mystery liquid off without some water, Lina got to her feet to walk inside. Just as she started though, her body flushed with heat and anywhere the clear fluid was resting began to itch beneath the skin. Panicking and worried the plant had shot some poison or acid on her, she ran for the house, sprinting past the pool that took up a sizable portion of the back yard and bursting through the door into the living room. She had to stop after getting inside, the sudden exertion making her head spin. She had thought the cooler temperature inside might help as well, but the heat and itching only got worse.

Blinking to try and clear her swirling vision, Lina stumbled forward, vaguely thinking she should get in the shower and pour cold water on herself. Aiming for her bathroom upstairs, she set off determinedly. Barely a dozen feet later, she collapsed onto a couch, gasping for air. Everything ached and she felt like she was melting from the inside out. Tears sprung from her eyes and she was half-surprised they didn't evaporate immediately. She was genuinely surprised to feel them take unfamiliar paths down her face though, changed from what she was used to all her life. And when they dripped off her chin and hit something else unfamiliar, the burning heat became a different kind.

A powerful thrumming took root in her abdomen and beneath her engorged nipples. She knew what it was: lust, strong and pulsing. Lina didn't feel it all that often, but wasn't above tending to her own needs when she felt the urge. Which usually came when she sloppily pasted her own face over Theresa's on the pictures that best displayed her larger boobs. She came hardest when masturbating to those, but what she felt now far outstripped even that.

The heat and pulsing beneath her breasts increased, each gasping breath she took alleviating it very slightly. The breaths slowly became more difficult and increasing pressure pressed down on her chest. Mustering her strength partially regained thanks to the gradually decreasing heat, she pulled herself up and, upon feeling a massively enhanced weight shift, looked down with bated breath.

She let out a surprised, disbelieving sob at the massive and firm breasts on her chest. No, not breasts, hefty boobs, mammoth jugs, big fucking tits. Enormous, overflowing, and more than she'd ever dreamed of having. Scrambling madly, she pulled out her phone and held it out to confirm what she was seeing.

No matter how she turned, her new chest moved and jiggled just how she expected from watching Theresa's, now comparatively smaller, pair. She grabbed one experimentally and nearly came on the spot, only suddenly aware of how much her lust had increased. Not to mention the plethora of other changes. Her face was gorgeous, skin immaculate, eyebrows thick above impeccably smoky eyes. Her hair was black as night and lustrous in the ****. Perhaps most delightfully of all though, her now pink shirt was perfectly fitted to her massive tits, leaving any of the unexposed flesh tightly wrapped in fabric.

Picture after picture were stored in her phone from every angle she could imagine, each one showing off her huge, firm tits to their best. She slowly started stripping out of her clothes, baring more and more of her glorious body until she was nearly naked. Testing the heft of her chest in her hands and to see how much they bounced and jiggled, she had a sudden thought. All but throwing herself towards the stairs (and having to suddenly compensate for her inflated rack), she ran up to her sister's bedroom and tore through her clothes until she found what she was looking for.

A black bikini. Too large even for Theresa's bust and which now looked too small for her own. It was the one thing she knew her sister was ashamed of buying, back when they were still growing and she had thought she would be the most beautiful and bountiful woman in the world. Once she realized that wouldn't happen, she had turned to making Lina feel inferior. But not anymore.

Bouncing giddily with her breasts nearly spilling out of the black swimsuit, Lina pranced down to the pool and slid herself in. She held her breath as the water flowed up to envelop her heaving jugs, prickling against the heated skin and revealing them to be ever so slightly buoyant. The gorgeous piles of fat floated just slightly in the water, making them look even more delightfully perky. Lina immediately posed in front of her phone, snapping away and coming up with dozens of sexy shots that showed off just how much her new body strained the bikini.

She flicked through them rapidly, finding her favorites with one hand. The other continued to heft, squeeze, and grab a tit, the low thrum of pleasure she felt slowly growing as she became more adventurous with her own body. Finally, Lina found her absolute favorite of the pictures she had taken, one with her sexy face perfectly positioned and tiny drops of water accentuating her enormous cleavage. She freed a boob from her swimsuit as she tapped away, quickly writing up a post to post and finally show her sister her place.

'Me and my new girls relaxing in the pool. Thanks to my sister Theresa for this awesome bikini, though it might be a little small! Being stacked is still way better than being flat though!'

Lina had to quickly put her phone down and jam her other hand down into her crotch as her nipple play threw her at the start of her orgasm. A few quick strokes to her clit and boobs had her cumming like never before, shockwaves of raw pleasure making her free tits wobble madly. She nearly passed out from the intensity of it, her vision darkening as she slumped against the wall of the pool. As such, the busty girl was oblivious to the small bits of milk jetting from her nipples and mixing with the pool water. The liquid dissipated quickly, leaving the water just as clear as before and laced with the virus. Anyone who entered the pool from now on would guarantee their own infection.

As soon as she could feel her hands again, Lina snatched up her phone and added an extra line to the end of her post.

'Throwing a party tonight to celebrate. Come by if you want a taste for yourself!'

She attached her address and posted it without a second thought before going back to playing with her tits, each one overflowing from her hands. Within minutes, people began commenting, either calling her new tits fake or saying they'd definitely be over for the party. Lina squirmed happily, for once thankful for her parents uncaring attitude towards their children. The only opposition she'd face for all of this would be from her sister, and her gushing quim already had a solid idea of how to deal with that.