One of my most memorable experiences occurred about 10 years ago, shortly after my wife and I married. We were 24 at the time, and my wife came from a large family - 4 sisters and a brother. Her youngest sister, Katie, was 16 and the 'baby' of the family. In fact, she was no baby - she was a VERY attractive young lady, with an amazing body; very large breasts (36C I checked her bra in the bathroom hamper), a great smile and a fantastic ass. She was the object of many of my fantasies since I first started dating my wife 4 years before, and she was a sweet kid who was very flirtatious. Several times she had kiddingly 'flashed' me by whipping up her t-shirt to show me her bra-encased boobs - hence the reason for my peek at her bra in the hamper (and several masturbation sessions with some used panties of hers I found in the same place.).
My in-laws had a place in the country where we would spend many weekends a year. On this particular weekend it was a small group, only my wife and I, Katie and her mom. Everyone else, including my father-in-law, was either working or had other plans. We arrived on Friday evening looking forward to a relaxing weekend of boating, swimming, dining out, etc. I was informed that 'the girls' would all be up early the next morning to go shopping but promised to be back by noon so we could hit the beach. In my devious mind I planned out the next morning - 'borrow' a pair of Katie's panties for an extended masturbation session since I would be alone.
I awoke about 9 the next morning with a slight hangover from the 5 beers I had the night before and a raging hard-on. I quickly hit the bathroom to take a wiz, and lo-and-behold on top of the pile of dirty clothes in the corner was a pair of panties - white bikinis with lace along the waistband, and little yellow roses for a pattern. I picked the up, took a whiff and instantly headed off to the living room for a long jack off session. I figured the plush couch afforded me the comfort and leg room I'd need to have the fun I planned.
On the way I grabbed a cup of coffee in the kitchen, checked to make sure all the blinds were closed, and then settled in. I was wearing only a pair of boxers, which I quickly slipped off and tossed aside. I took Katie's panties and began slowly sliding them up and down my hard cock, which of course felt blissfully sweet. I wanted this to last as long as possible, so my technique was deliberate and well-paced. My mind wandered to images of Katie - her previous 'flash' of about 3 months prior when we were in the car in the A&P parking lot while her sister (my wife) was inside getting milk. I thought of the last time I had seen her in her bathing suit (about 2 weeks earlier) - a beautiful one-piece black and hot pink suit that didn't do much for her gorgeous breasts but did an excellent job at accenting her firm, round and somewhat largish ass.
As I became more and more aroused I lost all sense of time and what else was going on in the house. I was shocked when I heard over my left shoulder 'OH MY GOD! PETE - OH MY - I'm really sorry!!!' It was Katie. I couldn't freaking believe it. The immediate thoughts that went through my mind were 1) I'm snagged, I'm dead, my wife is gonna freak when she finds out 2) What the hell is SHE doing here, she is supposed to be shopping, 3) How do I explain my 16 year old sister in law why I'm jerking off with her panties and 4) How do I cover up my hard-on with absolutely nothing to do it with.
In the split second all this went through my mind, I realized one-thing: while Katie sounded appalled and surprised and shocked, she was still standing there. She didn't turn away, nor did she make a move to leave. As discreetly as possible I put my hands over my crotch (still holding her panties.) and looked at her and said 'Katie, Jeez I'm really sorry.I thought you went shopping and I, um, well - was just kinda horny'. She was glancing between my crotch and my face, and she had a slight smile on her face. What she said next floored me.
'That's OK Pete, I know guys like to play with themselves all the time. I even saw Marc (her cousin) do it last summer down by the lake. But don't married guys stop doing it since they're having sex all the time?'
I hesitated before I responded, and realized we were starting this conversation with me still completely naked and covering my hard on with her panties. I noticed on the other end of the couch a throw pillow, and as I responded to her I leaned over, grabbed it and placed it on my lap.
'Well, yea I guess - but even though Sue (my wife) and I do have sex a lot, I still get horny and doing 'it' is how guys take care of it. I hope your not mad. Please don't tell anyone, OK? I would be SO embarrassed.'
She looked at me again and smiled and said 'Don't worry, I'm not gonna tell anyone. But I have to ask you something'. She looked down at my crotch, stepped forward and reached down. Oh my god - what was she doing?!?!? She touched my thigh - should I let her do this, I thought. Then she was holding up in front of me her panties - she had noticed, and they were still visible despite my efforts to hide them, and my cock, under the pillow.
'Why do you have my underwear?'
I had to think fast. Why? Why? 'Well, um - well, they're pretty sexy and, um it feels really good when I um.' I was beet red at this point, and very nervous.
'It's OK Pete. Don't freak out. I think it's kinda cool you think my underpants are sexy. I don't think anybody's every thought of me in that way before' How wrong she was.
She took a step towards the reclining chair opposite the couch. She looked at me and said, 'Can I please see you do it? I mean, can I watch? I promise I won't tell Sue or anyone, really. It's just, I think about guys and sex a lot, and when I saw Marc do it last summer it was SOOO cool and I couldn't stop thinking about it, and your cool and everything. Would it be OK?'
I thought about the ramifications - for about 2 seconds. She was a good kid, and I could trust her. So I told her sure. But made her swear that she wouldn't tell.
'I promise!!!' she told me.
I slowly removed the pillow and realized that I was still hard as a rock. Now without being a braggart, I will tell you I'm quite well endowed. About 7.5' and quite thick. Katie remained planted, standing in front of me about 3 feet away. She locked her eyes on my cock. She was still in her sleepwear - a pale blue men's oversized shirt that fell to the middle of her thighs, and I could see she had a bra on underneath. I assumed she also had on panties.
I slowly began to stroke and instead of remaining quite Katie wanted to chat.
'How does that feel'
'Do you do it a lot'
'Yea, a couple times a week at least'
'Do you orgasm when you do it?'
I laughed 'Oh yes, you'll see'
With that, she sat down on the recliner. She didn't sit back, but remained on the edge of the seat. She was directly in front of me, and her legs were slightly parted. I could see that she was in fact wearing panties, and I could see the crotch of them. I picked up the original pair I had begun the morning with and stroked my cock. After her questions she fell silent for a few minutes.
Then she spoke up. 'Do you mind, I mean I'm pretty horny too, can I - you know. Um, do 'it' too?'
YES! I was hoping for this. 'Sure, if you want. I won't tell either'.
With that she quickly unbuttoned her nightshirt and pulled it back. She was now in front of me with in just her bra and panties. She was obviously excited as her nipples were prominent even through her lacy bra. Her faced was flushed.
'Katie, can I see you with your bra off? I have always dreamed of what your breasts looked like'.
No words from her. She deftly unclasped her bra from the front and removed it through the arm of her nightshirt - quite a move! She threw it towards me and leaned back in the recliner, now just clad in the open night shirt and her panties. Her tits were gorgeous - firm, with large, brown nipples, large aereolas, and they were very hard. I picked up my pace as she moved her hand down between her legs and began rubbing herself through her panties, slowly at first but then more vigorously. I was in heaven. After only a few moments of this she placed her hand inside her underpants and began masturbating in earnest. Her eyes would close occasionally, and she was softly moaning while watching me. Our session continued like this for about 15 minutes - it took all my willpower to hold out that long! I could tell that she was also trying to make it last as long as possible. We both were reaching that point of no return, however, and as she got closer she pulled aside the crotch of her panties to expose her pussy to me!!! It was gorgeous - neatly trimmed, in fact hardly any hair at all, and very, very wet. Her middle finger was furiously rubbing at her clit, and she was moaning quite loud. Something overtook me and I stood up, went right in front of Katie and began to finish what I started. In seconds my orgasm began - 3 or 4 long streams of come shot out, landing first on her left breast and the rest on her stomach, arm, and legs. I convulsed for what seemed like forever as more globs of come bubbled out of my cock onto the floor. It was my longest, messy orgasm ever (then or now). I guess the sight of me coming sent Katie over the edge as she arched her back, squeezed her tits with her left hand, kept her right hand jammed between her legs, and she let out a small screech as her legs shook uncontrollably as she came.
As we both rested and gathered ourselves, she quickly buttoned up her shirt (despite the mess I had made on her) and I retrieved my boxers. I sensed she was feeling guilty, as was I. She was about to leave the room without a word when I said 'Katie, that was great. Did you have fun?'
'Of course. It was amazing. Promise not to tell anyone what happened, OK?'
'Our secret, for sure. You're OK?'
'Yea, fine. I'm going to take a shower' With that I watched her leave the room, and I went to warm up my coffee thinking about her awesome body and the beautiful scene I had just witnessed - a gorgeous, adorable 16 yr old girl masturbating in front of me.
That was 10 years ago, and Katie and I remain close. While we've never had another experience together, I have received my share of 'flashes' over the years (and not just of her breasts.) and still fantasize about her to this day.