Offline/Jerk off next to your sister
Looking down your body you can see, even in the darkness, the edge of your folded over sleeping bag lift ever so slightly when you flex your cock beneath it. You can also see your torso, one side of your bare pelvis, and most of your right thigh uncovered, but that isn't what's getting you excited. It's the sight of your naked sister once again plastering herself to your skin, her hands and head nestled into your shoulder, her cute lithe figure draped down your side.
It shouldn't feel like this. It shouldn't feel so good having your little sister's immature body pressed against yours so intimately. It should feel wrong shouldn't it? At least that's why you've been fighting it. But you don't know how something so wrong can feel so good. The first night was annoying, but now you want her next to you. Even just her hair brushing against your bare chest can make your cock twitch, but Emma occasionally wiggling her crotch into your hip as she gets comfy is maddening.
You wrap your arm around her in the same position as the last two nights. Although you tell yourself it's not your fault where your hand might end up tonight, you know exactly where its going to land when you reach squarely for her butt cheek.
A gentle squeeze of her right bum cheek encourages her to pull herself closer to you and push her right leg halfway on top of your own. Afraid you're being too obvious, you shift your hand up her hip and then palm her waist, but it's not like that's better. You're just feeling her whole body now.
Fuck. You're way too horny. That's gotta be all this is. Maybe it's your own fault for using your sibling as a nude model, but it was her idea, and you've been horny for days without relief.
Your left hand slides over your left thigh to secretly take hold of your cock while you are still debating with yourself and cupping your sister's ass. It's just gotta happen. And so it does.
Pinning your wrist against your pelvis, you stare straight up at the ceiling as you start methodically working the length of your concealed shaft. And it's amazing. Goosebumps crawl up your neck and tingles reach down to your toes. It's thrilling and terrifying to be doing such a thing, jerking off while your sister lays against you. To jerk off while groping her. And it's insanely frustrating knowing that your starting pace - though stealthy - can't possibly get you off.
You let out a long sigh as you quicken your pace, still working the full length of your shaft. Quick is relative though as you'd be lucky to be putting in a full cycle every second, but a bit of precum leaking onto your fingers is encouraging. Too encouraging.
Your pace quickens a little more and you let out another sigh. You know you're already close. Especially while gripping Emma's perfectly palm-able butt cheek. You don't need much. Just a bit of speed for a bit longer.
You look down to check out your progress, all but forgetting that your sleeping bag is covering your crotch. At least it's supposed to be. But then why can you see the tip of your dick?!
Pulling your shaft to the left, you curse yourself for not paying more attention. Either the bag shifted or your hand has been pushing your cock out into the open on each downstroke, but you take a moment to let your heart rate come back down before you adjust the flap.
"What are you doing?"
Your sister's secretive whisper, as if someone else might hear, makes you tense up. Did or didn't she see anything? Her face is angled downward the way she's curled up against you so it wouldn't be hard for her to catch a glimpse. But she SHOULD have her friggin eyes closed. Either way, it's not like you're going to tell her.
"Nothing."
"...nothing?"
"Yeah, nothing... Go to sleep."
A couple deep breaths help you take stock of yourself. Despite a flash of fear, your dick is still crazy hard and desperate for attention. That leaves you in the same predicament you started with.
So close and so far from satisfaction, you patiently pause a couple minutes to wait out your sister's curiosity, though you don't stop completely. You give yourself some long lethargic strokes, trying not to shudder while you keep the pleasure going, while hoping Emma will forget whatever she thinks she saw..
It's hard to say if waiting works. Your sister's small figure is quite stiff against you, unnaturally still, until she shifts herself calmly but warily. She pulls her left arm under her, between the two of you, and tucks her right closer to her body while still choosing to use you as her pillow. It seems like a less comfortable position for her, but she might be trying to make some distance between you without giving up her cuddle partner. You can't decide if it's good or bad that her warm soft pussy isn't smashed against you anymore.
Tension high, slow stroking rebuilds your resolve, which gradually works you back up to beating your meat rather than just teasing it. Hiding this from Em is still top of mind but your building excitement makes that difficult.
Doing everything the same as a few minutes ago unsurprisingly produces the same result. You watch with dread as the barely satisfying pace you need to get off also starts to edge your slippery sleeping bag off your crotch. What a traitorous bastard.
You can't just let it slide away. Your sister has remained mostly still since shifting, but she's clearly not sleeping either. So you pause again, sliding your hand off your dick and into the open to fiddle with the noisy polyester bag.
It's pretty futile though. A soft giggle lets you know you're failing to keep any kind of secret from your sister.
"That's not nothing."
"SHH!"
Great. Just great. She totally knows. What the fuck now?