Paradise Tease

My fiancé brings her crazy sister in law everywhere. She’s a cute brunette teen who is overly energetic. Bubbly personality, loves to talk, not really the type of girl I tolerate has a mouth on her. She’s handsy, clumsy, when we play around but ultimately sweet. We took a trip to a natural cascade nearby accesible through a steep climb and narrow rock trail. Our group decided to get in and hang out in a river bed underneath the falls. My fiancé pairs me with her sister who is begging to take the climb up with someone. I follow her sister through the trail, completely fixated on the amount of skin she’s showing. She’s removed her clothes revealing a matching string wrapped two piece bathing suit. Her ass has a nice shape, I’m enjoying the views as I am watching her climb a few rocks from behind. She has trouble gripping a smoother surface. I offer a push, she loses her grip. Slides down my crotch, visibly turning me on. Consequence of the warmth of our bodies together. We chuckle, I take the opportunity to hold her waist together and motion to thrust her up. My hard on digging into her ass, I push her up. Get a clear view of her bottom set digging in her ass. I somehow catch her from losing her grip again, this time with my hand on her butt. I’m pushing her up, meticulously splitting her ass open, I catch a glimpse of her stretched pussy. She lets out a slight yelp. I’m silently embarrassed, i apologize. She giggles, points out my strength. Couldn’t have timed things more perfect, her top randomly comes undone. I have a clear view of her tits, her eyes open huge. She laughs, I offer to strip naked with her to help with the embarrassment. Miraculously she agrees, and gets on all fours to reach the waterfall curtain. I’m probably the hardest man on earth now. Trailing behind inches from her tight slit. I high five her, the curtain is beautiful and loud. I look over she’s biting her lips hard clutching on to her swimwear. I offer to tie her top on, in case people show up. I crouch behind her, cock ready to penetrate once I tie her top. I’m fully prepared to ruin her. We hear people come up. Caught scrambling, we manage our bottoms on. I’m looking over the last corner, sigh of relief , a few minutes to spare. I turn around, a very devious look on her face guides my cock into her mouth. I’m playing with her warm throat. Don’t think they could here her gagging over the waterfall. She spit my load on some rocks before we trecked back. We don’t talk about it much. Being my sister in law, I know we both think about it. She pointed out how big I was. I think she’s scared I’ll pain her.