Incest Seduction/Sort yourself out
You're not really sure why she's giggling, but all this fooling around has got you hot and bothered. You can't help but chuckle too as you think to yourself Fuck it, I've got to take care of this thing now. Your hand slowly moves down and your fingers slip underneath your sweatpants.
Kim stops giggling and watches you with great interest. She had given you that boner, so it's only natural that she should be able to witness what you're about to do with it. As your hand slides all the way into your pants, you take a firm grasp of your rock-hard dick. Slowly, you begin to stroke your shaft up and down. You can't believe you're masturbating in front of your little sister! Until today, you always thought of her as your baby sister, but now she has clearly begun to blossom into a young woman.
From where she's sitting, Kim can't actually see your massive cock, but she can tell what you're doing with it. She watches you for a few seconds as you pleasure yourself underneath your sweatpants. You're avoiding eye contact with her because you're a little embarrassed by what you're doing, even though it feels so good. After a few more strokes, you notice out of the corner of your eye that she's making herself more comfortable, pulling herself a little bit closer to you. She lays her head back as far into the couch cushion as it can go, trying to get a better view. You don't necessarily want to expose yourself to her, but you're acutely aware of the fact that as your strokes grow longer, your sweatpants are being pulled away from your lap, and she can probably catch a few glimpses of your cock between gestures. Hopefully she likes what she sees.
Just then, you look over at Kim and notice that she has made herself really comfortable, having spread her legs apart. You look down at her crotch just as her tiny hand slips beneath her yoga pants, and she starts rubbing her teenage pussy. "Clit for tat?" you say quietly, but loud enough for her to hear. That's when she looks up at your face and smiles at you. Your eyes meet and you just stare at each other for a few seconds while you each vigorously rub yourselves. You can hardly believe that you're masturbating on the couch with your baby sister, and for a moment you almost lose yourself. You slow down your pacing so that you don't blow your load inside your pants. I'd rather blow my load inside Kim!, you think to yourself, but you're only about 99% sure you didn't actually say that out loud.
It's as if she had a telepathic connection with you, because that's when she closed her eyes and let out a rather loud moan. But rather than shy away from it, she just starts rubbing her cunt even harder. That's when you stop stroking yourself and ease off on the pressure. You just sit there in amazement as your little sister starts breathing heavily and gyrating her hips and pelvic muscles. As she moves her hand wildly about, you're able to sneak a peak down her pants and catch a quick sight of her hairless mound. It looks so smooth and inviting, and she is quite literally loving the fuck out of it!
By now she's bouncing up and down on the couch. Everytime her ass slams back down on the cushion, you're being rocked back and forth a little bit. That's when you realize just how close you are to her. Close enough that you could just slip your hand down there and take over for her if her hand gets tired. As she lets out another loud moan, this one even louder than before, your dick starts throbbing in your palm. You're not sure you can last much longer, but at this point what does it matter? Kim is clearly climaxing in front of you, maybe you should do the same in front of her. When are you ever going to have another chance to orgasm with your little sister? Possibly never.
So what do you do?
Stop pleasuring yourself and just enjoy the show!
You're doing laundry anyway, might as well get these sweatpants dirty too