Call your sister in. To apologise to her. Yeah.

"Jenny, can you come in here?"

Opening the door, your sister bounces - it's the only word you can think of that fits - into the room, hitting the door shut with her ass as she does so. It's hard not to stare. In deference to you she's put on a pair of loose, black shorts, or at least they'd be loose on anyone else. Her tits jiggle as she pauses in front of you as you sit on your bed, and you watch idly as a nipple threatens to poke out over the low-cut tank top. At this moment, you know you could see something close enough to it just by tugging your own top down, but something inside of you salivates at the idea of the dark brown point poking itself out into the open.

You kick yourself mentally. It's not as though you've ever thought about another woman this way, especially not your sister, but anyone with a body like that is going to draw your... attention. Yeah. Attention.

You realise that your sister is looking down at you. Her mouth twists as she controls a laugh. "Sure I'm not interrupting anything?"

It doesn't mean anything to you until you follow her eyeline down, past your own breasts (you have to lean back a little to do it) and gasp. Delving under the waist of your skirt, your fingers bulge the material outwards between your legs! Sometime during your fantasising you must have slipped your hand under there, and now you've noticed it you can't imagine how you couldn't feel the two fingers gently rubbing at your slit.

Blushing hotly, you start to pull your hand free, but quicker than you can think your sister has her own hand on your arm, holding you steady. You look up at her as she bends down to meet your eye level, a soft smile on her face. "Oh, Taylor, you know I don't mind... if you really wanted, I could even... help you out a little...."

Eyes wide, you begin to breathe a sigh of relief as she undoes her grip on your arm, only to yelp as her hand slides beneath your waistband and her own fingers start to rub between your legs. You try to wriggle backwards, but only succeed in pushing your wider hips down the bed, and with a giggle your sister inserts her fingers into you up to the knuckle. From then on any idea you have of escape is long gone from your mind, and by the time Jenny's straddling you and pulling her top off over her head you're just as eager to do the same with yours.

Her lips meet your nipples and you moan, throatily. God, this body just feels too good. The fingers toying with you as you're gently pushed to lie back on your bed send pulses of heat throughout your body, and the gentle caress of your sister's tongue against your tits shoots tingles across the long, arching curves of their weight. Jenny grunts in satisfaction as she pulls your own hand up to her - somewhere in the haze she'd lost her shorts again - and you find your own fingers teasing at her own cunt, **** to please as you're being pleased. You try your best through the mists of your own pleasure, but after a while of your clumsy efforts your sister lets out a hiss and slides herself down onto your fingers. A tiny voice tries telling you what you're doing is wrong, that fucking your sister must just be something that's happening because of whatever's happening to everyone, but a thousand other voices drown it out, demanding more, compelling you to lift your hips to meet Jenny's fingers, telling you how good it feels, two hot, wet sluts fingering each other frantically in your bed -

The first orgasm washes over you, and you shudder, your mouth opening to cry out with need. Your whimpering whine is only stopped when Jenny pulls free of your nipple and lift herself up to present her own to your open mouth. You don't think twice - you're beyond thinking once, just at this moment - and soon it's her moaning and shuddering around the fingers you're rubbing inside of her. She pulls off you, arching her back, and the sight of her shivering with bliss, huge tits bouncing wildly, is enough to set you off again.

It's the first joint orgasm you and your sister have. But it's far from the last.

When you wake again a few hours later, it takes you a while to understand why everything seems so off.

Then you look down at the humps in your blanket where your expanded boobs are, look across to see your sister dozing peacefully beside you, a contented look on her face, and it all comes rushing back.

The fact that the memories only serve to get you half-revved up again is swiftly ignored, and put down to you discovering, as you try to stealthily get out of bed, that your fingers still feel worryingly damp. With care, you slip them out of your sister, and trying hard to focus on feeling completely unsexy and not turned on at all, wriggle your own way off of hers, before carefully hopping out of bed.

Shivering a little, you look at your alarm clock while going through your cupboard for something to wear. Afternoon. At least you didn't fuck the day away, you tell yourself, cheeks reddening, planning for somewhere else to go partly to try and find out what's going on and partly so you don't keep finding yourself looking over at your sister's bared chest.

Maybe trying college would be a good idea - if people are going to gather anywhere, it'll be there, and they must have plans in place for.... well, not this, but... disaster, or something. You could always pick a friend's house. Someone far enough away that they might not have been affected by all this, but close enough to get to on foot.

You hear a tiny whimper, and turn back to the bed. Your sister's face is screwed up cutely; it seems like she's missing your hand on her, and even in sleep the bulge in the blanket that shows her own slides between her legs and starts moving against her. Against your will you start to feel your own lust building again, and it's all you can do to try not to drop the clothes you've gathered together and put your own fingers to better use, too.

You could always rejoin her on the bed, of course. You can think of a few fun ways to wake her up.