Offline/Try to redirect your sister's energy
You glance back down the trail you came from. It feels too risky to head back to camp, even though it's late, and especially if your sister is planning on getting naked once she gets there. There has got to be something more interesting the two of you can do.
"Yeah, I dunno about swimming."
Emma drops off of your hips and falls back onto her butt. "Why not?"
"Cause you'll prolly drown."
"Will not! YOUul be the drowny pants."
"Only cause you'd drown me when I hafta save you."
"Yur so stupid." Emma pushes herself back up to her feet, swipes her hand at you dismissively, then starts pacing about. "But it's soooo late, and erryone's asleep. What ELSE er we gonna do if we don't go naked swimming?"
"Skinny dipping."
"But that's what I wanna do!"
"No, you called it... nevermind. We can do whatever we want."
She smiles. "Like... swimming?"
"No, like better than that. Like what if we do... weird stuff."
"Like what stuff?" she asks, instantly interested.
"I dunno. Whatever we want. Buuuuut... I could finger your crotch again."
"Hahahaha! Ew!" Then Em stops pacing and thinks about it for a second. "Why dyou wanna do that?"
You shrug. "Something ta do?"
"You want to touch my privates!?" Emma laughs some more, then snorts. "You're so gross!"
"Like you didn't like it before."
She tucks a hand between her legs and laughs some more. "Ah course! You grossy gross face!"
You shine the flashlight on her as she wanders away from you toward the large clearing beside the cabin. "Is that a yes? Or you have a better idea?"
"...Only if you catch me."
She suddenly darts out of your beam of light, racing into the clearing. You give chase, your sister squealing and laughing as you bound through the tall grass together. Despite the fact that you should be faster, and you have a flashlight, your sister does an amazing job of evading you in the darkness. More than once she seems to disappear in a patch of especially thick foliage only to pop her head up a moment later running in a new direction. Whatever tricks she's using, she manages to stay ahead of you for several minutes before you finally tackle her.
"How're you so fast?" you ask, panting.
"Why you so slow?" she shoots back.
You assume the game is over now that you caught her but she tries to scramble to her feet to get away. You've got hold of her arm, and then her shirt, but she spins and twists and thrashes her way away from you. You've still got a firm grip on her shirt when you realize she isn't wearing it anymore. Once you clamber up and scan with your flashlight you find her bared back racing away, pale and bright and weirdly easier to spot than her shirt, her hair whipping about behind her shoulders as she cackles contentedly to herself.
Dropping her shirt, you continue the chase. Your sister is easier to keep track of now that she's topless, and you close in a minute later. You tackle her again, this time going straight for her leggings. You grip her skinny thighs and yank sharply. She kicks and flails and giggles, hoisting up on her underwear which start to roll down when her pants slide off her hips. She is happy to kick her way out of her pants, which is helpful considering you're forced to stretch them over her shoes. But she's up on her feet seconds later, ready to run again. You lunge forward, barely snagging the back of her panties, making her squeal and cackle. Yanking back even harder than her pants, you tug and tear them off in a couple quick motions and end up falling backwards onto your butt. Emma just laughs, apparently happy to be free of them, and keeps running.
Standing to give chase to your now naked sister, you realize that your flashlight is gone. You spend a moment pacing out a circle looking for it in the grass. If you dropped it then it must have turned itself off, or maybe the batteries popped out. You wonder if Em stole it from you, killing the light to help her escape. But as your eyes adjust to the moonlight you can't see your sister's little pale figure racing around anywhere. Her soft giggles are all that tells you she's still nearby.
"Em?" you call out, stepping slowly through the clearing. Straining to hear where she is, hoping she'll respond to you, you keep calling her name. The grass starts rustling and, when you turn, there she is, a naked little pixie leaping away from you. She runs a short distance then drops out of sight again. You race over to where you just saw her but she has either escaped or turned invisible.
You keep calling for her, trying to flush her out, but she continues to evade you. After a while it feels less like you are hunting her and she is instead stalking you. That suspicion is confirmed a moment later.
"RAWR!"
Emma jumps you from behind, sloppily grabbing you, failing to latch herself onto your back, and promptly dragging you down with her to the ground. She laughs and laughs, thinking she's hilarious.
"Happy now?" you ask, trying to dust yourself off as you stand.
"No! No!" she shouts, scrambling up. "I caught you! So it's my turn!"
Knelt in front of you, Emma continues to giggle as she fumbles with the front of your pants. You already got a semi from hunting your naked sister, so you grow even stiffer as your drunk sibling struggles to take off your pants. Whether from the darkness or her lack of coordination, she really does struggle. Soon she's jerking on the front haphazardly then grabs the sides and forces them down off your hips. She giggles even harder once your cock bounces up into the air, staring at it with a dumb grin while she inches your pants further down your thighs, as if drawing out stripping you so she can stare longer.
"Wait!" she abruptly shouts, stopping her giggles. "You need help! Don't you?"
You grin. "Are you gonna...?"
"I can get Sparkles!" she announces, trying to stand.