Offline/Grab your sis
You grab your sister's arm and yank her down on top of you. With one more motion you spin to the side, dumping your sis next to you on the edge of your air mattress and simultaneously sweep the flap of the sleeping bag over her body, pinning the middle of the bag down against the floor right as the door opens. Emma looks up at you, hugged tight to your chest, but you shake your head.
"Don't move," you whisper.
"Justice?"
You wiggle your free hand up past your sister's head and bring a finger to your lips, shushing whoever the fuck just opened the door. Blood pounding in your ears, your adrenaline dump in full swing, you confirm the voice of the intruder belongs to mom. You can tell the top flap of the sleeping bag is parted which might expose your sister's back. You really hope that the only thing peeking through is Emma's t-shirt and not her bare ass.
"Oh! Sorry!" mom catches herself, lowering her voice. She came in to wake you up, but thankfully she's willing to change her mind after your shushing. But she also frowns. "Why isn't she in her bed?"
"Cold," you whisper with a forced smile.
She gives a look of understanding then glances around the room. "Why is the window open?" she asks, a goddamn good question. "I swear I heard her talking."
"I... yaknow..." you mumble, shrugging and shaking your head at the same time. "She's weird." Emma pinches you in protest, but remains still.
Mom 'tsk's a few times but thankfully rolls with it. "Okay, well I know you've been skipping breakfast but I wanted to tell you we're making waffles with bacon and sausage and-"
"Umm, thanks. I'll... let her sleep though. Up real late."
"Alright. There's still time to change your mind. Just don't sleep the day away!"
You nod. Mom waves as she closes the door.
The pounding in your ears is slowing down. Emma stays frozen even after you let go of her and the bag. "She's gone," you assure her.
"Are we in trouble? Did she see... anything?"
You honestly mull it over for a moment. "No, I think we're okay. That was close though."
Emma is blushing really hard. She hardly looks up at you. "Your thing was poking me."
You push it down, already softening under all the stress. "Oh, yeah I'm sorry."
"It's my fault though," she says guiltily.
"No! Well, I mean, kinda. It's not a big deal."
"Okay, but it's still my fault."
"No. Em, it's fine. Really."
She sits up pushing the flap off your crotch and revealing your semi-inflated cock. She stares with a determined look on her face then slowly reaches out and grabs hold of your dick.
"Em..."
She lets go just the moment your mouth opens, pulling her hands back under her chin. "I just thought I should try to help... is that bad?"
"No, I just..." You shake your head, unable to fight your conscience. "This is weird. Way too weird."
You sigh and stand up so you can pace around the small room. Your erection is trying to make a comeback now, stuck at half-mast.
"But we need to rub it, right? That's what we did yesterday." She's talking like your cock has a pit crew.
"Yeah, but you can't just gr-"
"Then why can't I help?"
"Because we're not supposed to be doing that. Mom would ground us forever if she caught us."
She ponders that for a moment. "But she didn't."
You stop pacing and sigh again. "True."
There's only silence now. You wait for Emma to say something, but she doesn't. The awkwardness increasing, you grab your bag and pull out some clean clothes.
"We should probably go have bre-"
"What's it feel like?" she interrupts, her tone so sweet and childlike.
"Huh? Feel what?"
"What's it feel like when you rub it? You said it was fun."
"Oh. I dunno. It's like... like how you feel when I check you for slime."
Her eyes open wide, face going pale. She looks like she's just been caught in a dirty lie or ordered to death row. "Me...? I dunno wha..."
"Yeah. You like it, right? It feels sorta tingly, or whatever."
Your sister crosses her legs, a hand slowly sinking down between them. She looks down as you pull on pants, followed by a shirt, then looks up at you, eyes still wide. "So... it feels really good then."
You chuckle. "Yeah, I guess so."
"Well... you helped me, so... I should still help you," she reasons, her innocence crumbling further.
"Yeah, uh," Jesus. Can you even fix this? "Later. Come on. Get dressed."
She does as she's told, reluctantly pulling on a pair of overall shorts with stars on the front, a cute little faded pair she's owned for years that no longer fits her right and only works to belie her age. But as per normal you can't shut her up. Does it like the cold? What if you twist it? I heard a girl talk about sucking one once. Does yours taste how I taste?
You first contemplate gagging your sister with a sock, and then a cock, to shut her up as you walk to camp, but she's smart enough to hold her tongue once other people are around. Of course even holding her tongue manages to backfire.
Mom asks if there's something wrong with her after she doesn't say a single word through breakfast. You answer for her, explaining that she's tired since mom woke her up. Dad butts in, assuring that it won't happen again. He and mom share a glance, doing their telepathy thing, and thankfully that's the end of it.
You and Emma hang out with the rest of the kids after breakfast, chatting and loafing around. Eventually the group decides to go swimming. Since Emma apparently did forget to bring a swimsuit you leave her at the water's edge to watch everyone play while you head back to the cabin alone and get changed into your trunks. But when you get to the riverbank you see your sister frolicking in the water with your cousins, her overalls and shoes thrown onto the rocks. Auntie Grace, sunbathing despite the clouds, told Emma to jump in anyway; you only live once she said. Good advice. Some of your younger cousins are also doing the same, but where Emma kept her shirt on, two other girls are just in their panties.
You join in the fray, tossing the youngest kids around in the water and having crazy splash fests. There's one spot that has been declared as 'the diving board', a big boulder far enough out to be surrounded by deeper water but still close enough to shore to be safe. You all take turns cannonballing and diving into the river. Emma manages to jump on top of you at one point, forcing you to catch her. She then wraps her legs around you, locks her ankles, and starts giggling.
"Remember when you splashed me?"
You dunk her straight down, glugging and flailing. You have to. You could feel the blood rush into your penis the moment her wet panties squished against your body. You can't be rocking a stiffy surrounded by your sister and little cousins. Of course that's made more difficult when one of the girls loses her panties in the river a few minutes later, probably after a dive but you didn't see. She runs out of the water making a big fuss about it, turns to yell something at her own sister, then runs back to camp bare ass naked calling out for her mom and stupidly drawing as much attention to her nudity as she possibly could. If she didn't want people to see she could've just ran away.
Once you and your sis have your fill river fun and decide to get out, Auntie Grace offers a towel to your sister. Emma gets you to hold it up for her so she can change behind it with some modesty, but that gives you the only front seat view of your little sister peeling her wet clothes off of her slender undeveloped frame. She lowers her eyes bashfully, but doesn't turn away from you as she wriggles out of her soaked swimwear substitute. Once naked, she wraps herself in the towel and tries to walk away. Unfortunately your Aunt wasn't giving it to her, just lending it for her to dry off with. Confused, and not wanting to put wet clothes back on, your sis steps straight into her overall shorts instead. With nothing underneath however, the ‘all' part proves to be a misnomer.
The star-decaled patch in the front extends straight up from the actual shorts in a small square. Even if it was her current size the decorative patch likely wouldn't cover her chest, but as it is the thin straps have been pulled out to their longest length to accommodate Emma's creeping height. The cute but inadequate patch can only cover her stomach. Her dime sized nipples are lucky to stay hidden beneath the shifting shoulder straps which aren't connected in the back; they aren't even held together by a metal clasp. The independent straps connect with the shorts on either side of your sister's butt leaving plenty of space in between for the somewhat loose-waisted garment to flash the tops of her cheeks and the crack of her ass, at least when you peer down from above. And of course the sides are completely open leaving no shred of a doubt that she's wearing absolutely nothing underneath this thing. It's pretty paltry attire but apparently it's better than a wet t-shirt and pantie combo.