well...I've never told anyone this...while still in high school my cousin and I secretly took a shower together. she was a few years younger than I, but she actually pressed the issue.
on one afternoon, "mona" (i'll call her) and I got into a wrestling match on the couch. I was happily watching a college football game on tv, when she and my aunt came by so my mother and her could do some shopping together, and mona and I were to just hang back at my house. upon their arrival, mona ran in and jumped on me as I was sprawled out on the sofa. a little tussling ensued, then as I had her pinned on her left side, my hand came close to her mouth and she bit down hard on my thumb. through my squealing, I threatened to flick her breasts with my free hand, then felt her bite down even harder. I had both her arms pinned behind her back, but as I squirmed because of the pain, she was able to free her left hand just enough to get stuck up in my crotch. felling my penis brush against her wrist, mona reached up and squeezed my penis and pulled on it.
now, being a young boy, I became erect in her hand almost immediately. also, as I tried pulling away from her grasp, I noticed my penis sliding through her hand, so I jokingly humped against her hips a few times. the look on mona's face was priceless...I begged her to let go, then quickly thrust against her a few more times. except, now her hips have rolled just enough that as I thrust, my erection slid trough her hand and along her upper thigh.
at this point, I pleaded for her to let my thumb go because how painful it was. finally, mona released my thumb then I stayed pressed against her as we inspected her incredible bite mark that almost broke the skin. moments later, we realized that she still had a grasp on my still erect penis, so I grabbed her hip and thrust against her again. giggling, mona let go of my erection, rolled onto her back, then coyly asked if she could see it. nervously kneeling between her legs, with my erection jutting out from my gym shorts...I said "only if you take a shower with me, so I can see you too." 100%, I fully thought she would refuse, but jumped up and led me to my bathroom.
I started the shower, quickly undressed, then got in the shower. mona took a bit longer, but eventually stepped in behind me. I remember feeling her warm pointy nipples touching my back as she hugged up on me from behind. then the incredible sensation of her dainty hands running down my stomach to my already swollen penis. I stood there marveling at her hands exploring my hardening cock, when I felt her pubes tickle my ass as she bent around my side to watch herself fondling my penis. moments later, I coaxed her in front of me, and stood there stunned by her nakedness as the water glistened down her curves and through her dark pubes. we made eye contact, and I noticed her blushing with embarrassment when she thrust her arms around me in a tight embrace. I slowly slid a hand down through her pubic hair, and after a few short strokes, mona became wet then let out a low breathy moan as she wrapped her arm around my neck. I rubbed faster and asked if she had ever had an orgasm. she had not. a few minutes into this, I backed away from her slightly, then guided my penis tip down to her clit. with her hand still on my cock, I rubbed my tip against her clit for a moment, then turned her around. at first, i just reached around and rubbed her fast, slow, and hard at times...eventually, mona began to really get into it, so i got the idea to slide my erection between her thighs from behind. with her wetness, i slid through her legs with ease as i slowly thrust against her while rubbing her hardened clit. not taking long, i became overwhelmed with my own impending orgasm and abandoned her clit for grabbing her hips and thrusting faster through her soaked thighs. i told her i was cuming, pressing against her ass as hard as i could, we both watched my cum jet out of my penis as i convulsed between her thighs.
looking over mona's shoulder, i could see a little more than the tip jutting through her pubes as i spewed my load through my cousin's thighs. mona covered her mouth with one hand and involuntarily rubbed herself as this goes on, then giggled...saying "holy shit! wow"
we ended up staying in that position for a while, because my penis never softened. i resumed rubbing her and slowly sliding myself through her thighs, until i a came again. unfortunately, i wasn't able to give mona her first orgasm, but to this day i can hear her moans while i masturbate to that experience. we never talk about it, and have never done anything further together, but every once and a while mona will make a comment that leads me to believe that still thinks about it like i do. at least that's how i take it, because i still fantasize that more has happened or more can happen. unfortunately, mona is not as attractive now, but should she initiate anything...i will be game.