BEHIND THE SHED

 "You're sure about this?" I asked hesitantly, crouching next to my younger sister behind our shed in the backyard.

"Positive," Bree said, fidgeting nervously next to me.

We were both eagerly watching and waiting. Our older sister, Marie, came around the corner just then, in her running outfit on the way back from her normal morning jog. She was a fitness buff, always had been. And her body showed it of course. She was the tallest of the three of us, with a very thin frame and long blonde hair. Her skin had a nice tan to it, from all the running she did. She was always outside it seemed, doing something to keep active.

"Here she comes," Bree whispered.

We were hidden from view, but could easily watch as Marie rounded the corner of our yard and ran into the backyard. She slowed her pace and came to a halt at the back patio, catching her breath and then stretching her legs after her two mile trek. I couldn't help but notice as she stretched that her body was really amazing. Even though she had a thin frame, she wasn't exactly lanky. Her butt especially was really toned and nicely shaped, and even though her breasts were small they seemed to fit her body very nicely. Overall, she was a very sexy young woman.

After stretching for a bit, she seemed to glance around to make sure no one was looking. Thankfully, Bree had suggested this particular spot because it wasn't very visible. There was a tree between us and the patio, and unless you were specifically looking past it, you wouldn't notice the shed or anyone hiding behind it. Marie went around to the side of the patio that was actually a bit closer to us now, and for some reason she leaned up against the house there and just waited for a moment.

I still wasn't sure what Bree had dragged me out here to see. She came to me the other day and said she wanted me to see something. She wouldn't tell me what it was, but she said I had to see it to believe it. Bree and I were a bit closer than either of us were to Marie, being as she was the oldest. Not that any of us didn't get along. Marie was two years older than me, and Bree and I were less than a year apart. I guess naturally we just seemed to have more in common. We had been in the same grade all through school even. Marie was the typical older sister, kind of bossy but also protective of us when we were younger.

"Don't say or do anything when it happens," Bree warned me.

"When what happens?" I asked.

"Sssshhh," was her only response.

I moved closer so I could see better, and ended up rubbing my crotch right up against Bree's shoulder. She didn't say anything, and I didn't think much of it because it wasn't like I was going to get aroused and start poking her. I was just trying to get a better view of whatever she was here to show me.

Marie started to rub at her stomach, and for a moment I thought maybe she was sick. But as I watched in disbelief, she starting to pulled down her running shorts right there in the yard and revealed to us both that she wasn't wearing anything beneath them. My mouth dropped open, but I kept quiet like Bree had said. What in the hell was Marie doing in our backyard out in the open?

"Just watch," Bree whispered. "It gets better."

Marie left her running shorts down around her knees, and even from this distance I could see that she shaved her pussy completely bare. I couldn't believe she would be so brave out in the open like this. Was she an exhibitionist or something? I kept glancing around, nervous for her that someone would be able to see her. But in the spot she had picked, none of the windows of our house were within view. And because of our trees in the backyard, none of the neighbors would be able to spot her either. She had found a spot in our yard that was completely invisible to anyone not standing near there. I guess since our parents were at work this time of day, and my sister and I were typically in school too, she wasn't worried about someone coming to catch her in this little sexual escapade of hers. But since Bree and I had already graduated this year, she either wasn't accounting for our presence or she figured we wouldn't be bothered to spy on her.

Somehow Bree had discovered what she was up to. I wondered how long this had been going on exactly. Marie closed her eyes and started rubbing at her pussy, taking her time and quite obviously enjoying herself. Once I got past the initial shock of it all, my fascination with the whole scene took over and I started to get aroused.

"Hey!" Bree hissed, nudging her shoulder against me. "Ew, Kevin. Gross!"

I had started to get hard in my shorts, and ended up poking her with my dick. I couldn't back off of her without making too much sound though, and neither of us wanted to be caught.

"Sorry, but I can't move now," I said. I was only a little embarrassed, since Bree had caught me masturbating before. A couple of times actually.

"Just, try not to hump me ok?"

We both sat there like that, watching as our big sister masturbated in the back yard in her own little private seclusion. Why didn't she just do that in the house, in the bathroom or her bedroom? She must get off on being outside, or maybe the thrill of being caught was part of it. I'm sure that thrill didn't include her siblings finding her like that. But it did make me wonder what other kinks she was into. I never thought of Marie even having sex. She rarely dated, and was usually so uptight about everything else that I just assumed she was a prude. I guess I was wrong.

I had to admit, it was odd that my erection was pressing up against Bree, and that she wasn't freaked out by it. I couldn't keep it from tensing up a few times, and I know she noticed it. But she didn't say anything, we just watched as our sister quietly masturbated for a few minutes until she whimpered and thrust her hips forward a bit, slowing her fingers on her clit and dropping her head down in pleasure. She really seemed to enjoy her climax, and rubbed at her mound slowly and firmly for a bit more as the feeling washed over her.

Wow, that was really hot! And thinking about Bree watching her at least one other time was also arousing, though I wasn't sure why. These were my sisters, after all. This kind of thing wasn't exactly proper.

Marie pulled her running shorts back up and dashed off into the house, as if those few minutes of sexual pleasure never happened. After she was gone, Bree looked up at me with a mischievous smile.

"So, what did you think?" she asked.

"I can't believe it!" I answered truthfully. "How often does she do this?"

Bree moved away from me a bit, finally withdrawing herself from my erection pressing against her. But she didn't say or do anything to suggest she was grossed out by it anymore. I was still tenting quite obviously between us still, but she pretended she didn't notice. At least, for the moment.

"She's done it the last three days," Bree said. "I caught her doing it last week, and I've been coming out here to watch ever since. I figured you'd wanna see it for yourself."

"I can't believe she does that," I said. I absently squeezed at my boner beneath my shorts, forgetting for a moment that my own sister was standing next to me. My mind was still on the scene we had just watched.

Bree glanced down to see me do it, and then giggled. "A little too much to handle, huh? Perv."

I blushed. "Hey, you're the one who's been spying on your own sister masturbating."

She nodded. "Yeah, I don't know why, but it's really hot. I'm not into girls or anything, and especially not Miss Perfect, but it's fun to know we have this on her, isn't it?"

I shrugged. "Yeah, but if she ever found out we were watching her, she'd freak."

"Oh, of course," Bree agreed. "I'd never tell her. Or anyone besides you. I'd suggest you don't tell anyone either, even your stupid friends."

I was still squeezing my boner through my shorts, feeling way more aroused than I should've been considering how inappropriate this all was. Or maybe, that was why I was so aroused. Bree just stared at me as I did it, and I couldn't look her in the eye. I wanted to move, but she was in my way.

"Are you..." she began. "You're gonna go jerk off, aren't you?"

I was so embarrassed, my erection should have been non-existent. But this whole situation was somehow really sexy, and I felt ashamed that my own sister was here to see it. Of course, was this any different than us spying on Marie playing with herself? The whole thing was really confusing, but apparently really hot.

"It's ok..." She seemed to hesitate to say the words, like she knew it was normal to masturbate but since this was her own brother she was talking to, it seemed wrong to admit it. "I mean, we all do it, right?"

I finally looked at her, and she seemed just as nervous as I was. But there was something else too. Something...perverse in her eyes. Her jaw cocked to the side just a bit, and I could tell something naughty was bouncing around in her head. I knew that look of hers, but had never associated it with sex before.

"What?" I asked.

She let a smile creep across her mouth, but was quick to hide it. "Uh, nothing. Just..."

"Just what?" Shifting the focus onto her seemed to ease my nervousness, and embarrassment.

Bree fidgeted, standing only a few inches from her aroused brother with his dick tenting out in his shorts. Her manner when she got like this, playful and devious, drove me wild. I only secretly admitted to myself that I was attracted to Bree. She was shorter than me, with reddish blonde hair and the cutest freckles dotting her button nose. When her full lips would purse into that devilish smile, it just got to me I guess. And her eyes would say more about what she was thinking than any other part of her, even that cute mouth.

And, her body was nothing to scoff at. She was thin like Marie, but with just a bit more curves to her. Marie was like a stretched out version of her, with less ass and chest. Bree had a nice set of C cups, more than decent for her tiny frame, and her butt was perfectly round and taut.

"Are you?" she repeated.

I just eyed her, cautious yet not entirely put off by the thought of telling my hot younger sister that I was going to go upstairs to my room and pull on my wiener until white stuff came out.

"Maybe," I said finally.

"Well, isn't turnabout fair play?" she said, with that sexy little grin.

"You want to watch me," I said, "because we watched Marie?"

She nodded, turning red but not averting her eyes from me. She waited, obviously teasing me. But for some reason, it made me want to show her up. And besides, she had seen my dick before.

"Fine, you little twerp." I yanked my shorts down and let my cock spring free.

Her eyes widened, but she didn't point and laugh or even get all embarrassed. Her smile faded and she just stared openly at my penis. I could tell that she was aroused by it, and that made it lurch.

"But you better give me a show too," I said.

Bree looked up at me finally, and then glanced around. "I don't know if I could do it here. I don't...get off the same way Marie does. I have to be laying down."

"Fine, but you owe me," I said, and grabbed my dick firmly.

So there we both stood, both of us watching my dick as I jerked it. Bree was positively entranced by the sight, and I found myself sneaking glances of her while I beat off. It was sexy, there was no doubt, to be doing this while a cute girl watched. And the memory of seeing Marie touching herself was still vivid in my memory. Both of those images seemed to get me there much sooner than I anticipated. I slowed in my movements, not wanting to bust right away.

"What?" Bree said, her voice raspy. "Why did you stop?"

I grunted. "I...was about to cum."

She looked up at me and shook her head. "Good, do it!"

I guess I was embarrassed about it, but it seemed silly considering. For some reason though, cumming in front of her seemed to add finality to this naughty act, and when it was all over we both might feel bad about it. The forbidden aspect of being brother and sister had spurred me on before, but now it hindered me from wanting to finish.

"Do you want to cum in my hands?" Bree asked.

I pictured jerking my big cock off into her little hands cupped and held out to catch my sperm. The mental picture was just too much, and I quickly beat myself off again. She took that as a yes, and held up her hands just as I pictured she would.

"Ugh!" I grunted, and felt my balls churn. I aimed my dick carefully, not wanting to shoot off all over her, and let it cum.

It didn't happen exactly as I had pictured, with my dick calmly spouting gentle streams of semen into a nice neat little puddle in Bree's palms. Instead, I exploded up her arm on the first shot, and the second tagged her t-shirt on the edge of her breast. The rest of my spewing was easier to maintain, but I fired off six or seven powerful spurts, and it felt better than anything I had ever felt before. Bree excitedly tried to keep from moving, even though I had painted her hands and arms. She just held them up, waiting for me to finish.

When I finally was, I lost all sense of embarrassment or shame. It was the opposite of what I had feared. Now that it was over, it felt good to be sharing this intimate part of myself with her. She smiled as she examined the mess I had made, and I squeezed my dick and sighed.

"Wow, you came a lot," she said.

"Yeah, sorry. I tried to keep it all in your hands."

"That's ok, it was so hot!" She seemed enthralled with my cum all over her.

"You better go wash up," I said, stuffing my still-hard penis back into my shorts.

She nodded. "Hey, um, how often do you do that?"

"Every day," I answered truthfully. "Why?"

"Well..." She seemed to be hesitating to ask what she really wanted to. "That was really cool, is all."

I could sense that she had been excited by this naughty little escapade. And maybe she would want to repeat it, I hoped.

"Want me to tell you when I do it again?" I ventured.

It could have been a risky question, if in fact she regretted all this. But my instincts hadn't failed me. She nodded enthusiastically.

"Yeah, is that ok? I mean, you liked it, right?"

"It was awesome," I assured her. "And you still owe me."

She really lit up at hearing that. "That's right! I do! I'll give you a great show later tonight, ok?"

Later tonight, our parents would be home and we wouldn't have much privacy. I couldn't just be seen going into her room and locking the door, or vice versa. They, and Marie too, would be suspicious.

"I don't know..." I was reluctant now, even though the thought made me stay hard in my shorts.

"Please!" Bree begged, like a little girl asking for candy. "We can wait until everyone is asleep."

"Ok, but we have to be careful."

She clapped her hands. "Thanks, Kevin!"

She trotted off, still covered in my cum, and went to get the hose. I just stood there for a moment, wondering if we could really get away with this. Staring at her cute little body as she washed herself made me forget most of my fears. And, there was still the matter of Marie. Bree and I could keep coming out here to watch her, and maybe I could even get off at the same time. Watching Marie and being watched by Bree was really hot to think about.

I quickly went inside to my room, where I took a cold shower to keep from jerking off again.

Chapter 2

That night couldn't come quick enough. Once everyone went to bed, I waited in my room until it was well after midnight. Then I tiptoed down the hallway to Bree's room and quietly opened her door. Her light was off, and it looked like she was asleep. But when I approached, I could see her turn her head toward me.

"Kevin?" she whispered.

"Hey." I closed the door behind me and approached her bed.

She sat up, looking excited even in the dark. "We have to be quiet, Marie will hear us through the wall."

My sisters shared a wall between them, and it just so happened that their beds were parallel too. Bree was right, if there was squeaking or lots of groans, Marie might hear.

"So, what are we gonna do then?" I asked.

Marie thought for a moment, biting her finger nervously. "Um, I promised you a show, so I guess I'll get naked."

It was dark but not too dark to see as Bree took her camisole off and then slid her pajama pants down past her ankles. Without hesitation, she had stripped completely naked before me, and I could see everything. I guess that was the point. Her tits looked awesome, better than I imagined they would. Her pussy wasn't bare like Marie's had been, but it was neatly trimmed.

"What should I do?" she asked, seeing me eyeing her body up and down and not trying to hide anything from me. She apparently liked that I was so attracted to her.

"Should we...do it together?" I asked, realizing I hadn't planned what to do before coming here.

"Sure." She seemed fine with that, eager actually. "Come sit next to me then."

I pulled my shorts off and joined her. We were both naked on her bed now, and even though it seemed a little weird, it was mostly just hot as hell. I was at full mast already, and Bree noticed. She eyed my dick, and her hand drifted down to her crotch.

"Go ahead," she encouraged. "Just do whatever you want."

I grabbed my dick and slowly started stroking it. It would have been better with the light on, but someone might notice. I had to settle for how it was right now, and even so it was hotter than anything I had ever seen online or in person.

Bree's tits bounced just a bit as she began rubbing her clit in a more purposeful motion. She didn't really start out slow like I was doing. She seemed to get right to business. Our legs were touching as we both laid there, eventually settling into our normal individual routines for this kind of thing and just doing what came natural. It felt really good to be this open with a girl, and to let her see this side of me. I had never ever masturbated in front of anyone, except for her earlier today. It was intimate in a strange way that seemed better because we were close siblings.

Bree climaxed very soon, long before I would even get close. She whined softly, and her hips came off the bed a bit. She humped into her hand and her eyes were closed tight as she rode it out. I kept stroking as I watched her, but it would be a good while longer before I was ready to blow. She relaxed and opened her eyes, sheepishly looking over at me but not missing a beat as she went right back to rubbing her cunt.

"That felt good," she breathed.

"It looked like it," I responded. "You cum quick."

"I was really horny," she admitted with a smile.

That seemed to get me off even more than the visuals of my cute sister masturbating. Knowing my cute sister got off on seeing me masturbate was really arousing. I jerked faster and gently rubbed under my balls as I did so.

"Where do you usually cum?" she asked me, more focused on me now than herself.

"On my stomach," I said, huffing a bit. "Depends on where I'm doing it."

"Where are all the places you've cum?" She was very interested now.

"On myself, a kleenex, trash bin, an old shirt, the toilet, the sink..." The list went on and on, but that seemed to be sufficient to satisfy her curiosity.

"Wow," she said, and she put two fingers into her pussy just then. "I can only cum when I'm stretched out and totally relaxed."

"You just need to practice," I said, really getting into my jacking.

She noticed, and she started grunting a bit as she fingered herself more urgently. We were both getting there, and knowing that only fueled us both.

"I...do it a lot," she said, starting to pant. "Almost every day."

"Mmm...well, maybe...uuuhh...you should try it in different places."

"Like where?" Her hips thrust upwards, like she was really close.

Let's try it again tomorrow," I said, feeling my balls tighten. "We'll watch Marie, and do it behind the shed again."

She cried out just then, a bit too loud I thought, and climaxed again. I squinted as my dick started spewing all over myself. She noticed as her own orgasm finished, and she beamed brightly at seeing my torso covered in streams of white.

"That is so cool!" she whispered.

I smiled, and breathed a sigh of relief. That had felt good, even better than before. And, I came a lot even though I had drained myself already today. I just kept stroking, letting the good feelings trickle throughout my body. Bree absently rubbed her mound and stared at my dripping cock as I touched it.

"We need to do this again," I said. "Like, as often as possible."

"I agree," she chuckled. "It feels way better when someone watches you."

Suddenly, our legs touching seemed like it was too tempting, and I moved to get off the bed. I wasn't embarrassed or regretful, it just seemed like it would be easy to cross another line that we weren't ready to cross. Bree didn't object, and I think she just thought I was ready to go to bed.

"Thanks," she said. "Remember, eight o'clock tomorrow. Set your alarm."

"I will." I left her room and returned to my own, barely remembering to grab my discarded shorts on the way out.

I slept really well that night, but my dick was pointing at the ceiling the entire time.

Chapter 3

"Sssshhh," Bree hissed at me as I approached. "I think she's coming back already."

I hurried to hide with her behind the shed, and this time our bodies pressing up against each other didn't bother her. We quietly observed our older sister Marie return from her jog, just like yesterday, and find her secret little spot after stretching her legs.

I started to loosen my shorts, and Bree seemed amused.

"Already?" she whispered.

"Come on, you need to try it," I replied.

She was reluctant, but remembered what we had agreed. She would try to masturbate in places other than her bed. She reached into her own shorts and started fingering herself, though she left them pulled up.

We both watched as Marie did her usual routine, pulling her running shorts down to her knees and rubbing her slick cunt for a good few minutes before having a nice orgasm. This time though, she didn't seemed content with just one. Even though it had been obvious she had climaxed, she kept rubbing. From her reactions to her own fingers, I could tell she was more sensitive now. Maybe the second one would be even better.

"Oh my god," Bree whispered so quietly that I barely heard her. "She's so horny."

I grunted, and had to stop jerking myself to keep from spewing prematurely. Bree noticed, just like before, and this time took that to mean she needed to catch up. Either that, or the thought that I was close was getting her off even more.

She started grunting, making small sexual noises, until her hand suddenly stopped her frantic movements and slowed to a crawl. She seemed to have a hard time staying in place as she crouched beneath me, and I could finally see that she was having an orgasm.

I was proud of her, and simultaneously aroused to the point of no return. I started cumming, and wasn't entirely aware of where I was about to shoot. I splashed a stream of white across her hair accidentally, and managed to pivot to shoot the rest onto the side of the shed. I don't think Bree was even aware of what had happened, she was so lost in her own pleasure.

Marie finished getting to her own orgasm, again, and seemed satisfied now. She pulled her running shorts up, and my attention turned to Bree fully now. She was still crouched below me, but was feeling cautiously at her hair.

"Kevin!" she said. "Oh my god, really?"

"Sorry." I didn't bother to stuff my dick back in my shorts, and just watched as she tried to peel the stream of cum from her hair.

Realizing it was a lost cause, she yanked her t-shirt over her head, and to my surprise she had no bra on underneath. She was bare-chested and using the shirt to clean up the mess I had made. It must have looked really funny to see me with my dick hanging out, and her rubbing the shirt on her head with her tits hanging free.

Funny, or shocking. I could easily tell which one Marie thought it was, when she suddenly appeared right in front of us next to the shed with wide eyes.

"Kevin!" she exclaimed, then she turned to Bree. "Bree?!"

We both froze, and just stared back at Marie. She was still in her running outfit. She must have heard us before going inside. Crap, we were totally busted now. And we couldn't have been in a more awkward position.

"What the hell?" she yelled.

Bree quickly covered herself with her soiled shirt, and her hair was a comical mess. But no one was laughing right now.

"Uh, shit..." She stammered to explain. She kept glancing from Marie to me and back, but I had nothing to add. I was so dumbfounded I didn't even put my dick away. I just held it there, dripping a string of cum from the tip. It was obvious by the splatter next to me on the shed what I had just done.

"What are you two doing?" Marie demanded.

"We were..." Bree was really struggling to come up with something.

"Were you two spying on me?" Marie said, her voice full of shock and embarrassment.

We just stared back at her, our deer-in-the-headlights look answering her question. I suppose my dick and Bree's tits told the rest of the story. Maybe Marie thought we got so aroused by our voyeurism that we started in on each other. She probably wouldn't have guessed that we were just playing with ourselves and not touching each other at all. I felt like reassuring her that this would be the correct assumption.

"Yes, we were," came my response finally. Bree shot me a look.

Marie was flabbergasted. "I can't believe you two! Are you...having sex?"

Bree shook her head in protest. "No, Marie! Honest!"

I finally got the courage to pull my pants back up and face my older sister like a man.

"We didn't touch each other," I agreed. "We were spying on you, it's true. We just got so aroused by it that we couldn't help ourselves. It's my fault, Bree was just playing along."

Marie was so angry that she couldn't even get her words out right. She just shot another glaring look at Bree, and ran off into the house.

When it was just the two of us again, Bree gave me a look of terror.

"Do you think she'll tell Mom and Dad?" she asked me.

I shrugged. "If she does, then wouldn't she also have to tell them what she was doing?"

Bree seemed relieved at this realization. "Yeah, you're right. She wouldn't want them to know what little Miss Perfect does in the backyard."

She put her shirt back on, and I got a good look at her tits again before they were covered. Her shirt had a big stain across the arm now, where she had wiped at her hair.

"I'm...gonna take a shower," she said, and made to leave.

"Wait." I grabbed her arm to stop her. "What about...us? Are we ok?"

She smiled. "Yeah, don't worry. We probably won't be able to do this again, since I doubt Marie will ever be playing with herself in the backyard after this. But we can still play."

She winked at me, and ran off inside. I stayed there for a few moments, trying to compose myself. I wondered what was in store for us now with Marie...

Chapter 4

Dinner that night was, well, very awkward to say the least. Marie was fuming, but didn't say a word to anyone while we ate. Mom and Dad mostly talked between themselves, not involving us kids much in the conversation. Bree and I must have looked as guilty as we felt, and Marie was staring icy daggers into us both. But, like we had guessed, she didn't squeal on us. That would have meant squealing on herself, and as much as she probably wanted us both to suffer, she didn't want to look bad either.

Afterward, Bree and I went into the living room to watch TV, while Mom and Dad said something about going to bed early. That usually meant they were going to have sex, which we couldn't care less about really. Marie took this as her opportunity to confront us.

"Both of you," she said, standing between the kitchen and living room in her camisole and pajama pants. She must have changed clothes just moments ago, which was a bit strange. "In the basement, now."

Bree and I exchanged looks, and Marie didn't wait for us to respond. She turned and headed downstairs to the basement, and we were helpless to refuse her. Better to get this over with than to keep feeling guilty and avoid her.

We trotted off after our big sister and the three of us were now face to face in the basement. It was mostly finished, with carpet and an old couch and some bean bags. Best of all, it was the bottom of three levels in our house, with all the bedrooms upstairs, so it was totally private when Mom and Dad were upstairs getting it on.

Marie sat on the couch cross-legged, while Bree and I each took a bean bag chair. She eyed us carefully, but she seemed to have calmed down quite a bit. Neither Bree or I could look her in the eye, though.

"Ok, look," Marie began. "We all know that none of us should have been doing...that, outside in front of each other."

Bree sheepishly nodded, and I just sat there saying nothing.

"It was wrong of you two to spy on me," she continued, "and I'm very embarrassed to have been caught. But, I feel like since we all share some of the blame, we should just come clean, and I should explain why I was out there in the first place."

Bree seemed to light up a bit, and chanced looking up at her big sister. I just watched Bree, waiting for her to respond positively so I could then attempt to look Marie in the eye.

"We all...masturbate, right?" Marie asked, and waited for us both to respond. Bree nodded, and I did as well. "Good, there's nothing wrong with that. It's not a big deal that we all do it. It's a private matter, and it doesn't hurt anyone."

"Why were you doing it outside?" Bree blurted out, not waiting for Marie to finish her explanation.

Marie's nostrils flared, but she didn't lash out. "It's kind of embarrassing, but I guess I should explain so you don't think I'm a pervert or anything. A while ago, after my run, I came home and took a hot bath because I was so exhausted, more than usual because I went farther than I normally do. I started to...touch myself, and of course ended up...well, finishing the act. And I noticed that when I...ahem, arrived so to speak, it was better than normal. I just thought maybe it was the hot bath. So I took another one the next day, and...masturbated then too. But it didn't happen again."

It was bizarre to hear Marie talking about this, and saying those words. I found myself getting aroused, but I wasn't about to let either of my sisters see my shorts tenting.

"So," Marie continued, "the next time I did a particularly exhausting run, I took a shower and ended up using the shower head on...myself. And again, it was a really good...orgasm. Ahem. So I did the same thing the next day, including the run, and it was really good again. If my run wasn't very long, or if I didn't run at all, then my orgasms weren't as good. I realized that it must be the adrenalin from my intense runs that was making it so good. And the closer to the end of my runs I did...it, the better they seemed."

"So you're an adrenalin junkie," Bree said. I just kept quiet, but I was very interested.

"So to speak, I guess," Marie replied. "Lately, I've been trying to figure out when they are the most intense, and it does seem that right after my run they are really good. So I found a spot that I thought was private in the yard and I kept doing it."

"But, why do it outside?" I finally spoke up.

Marie seemed uncomfortable, but didn't dismiss my question. "Yes, well I suppose you deserve to know why I do that, even though I should just be mad at you both. But I guess I was just asking to get caught eventually. The truth is, I do find it kind of arousing to do that outside. I don't want to be caught, but the thrill is a little exciting. And when I'm really excited, mixed with the adrenalin, my orgasms are even better."

"We noticed," Bree said. "You did it twice in a row today."

Marie shot Bree a look, but again, how could she really be mad at us? She was the one who was acting deviantly. But Bree and I masturbating together while we spied on her, though, was a different matter. And one Marie chose to bring up finally.

"Now that I've explained myself," she said, crossing her arms, "now it's your turn. Both of you. What exactly is going on between you? I can't believe you'd both be masturbating together behind the shed unless there was already something going on."

Bree shook her head. "We aren't screwing, Marie. Honest."

Marie looked at me, waiting for me to agree. I nodded enthusiastically.

"It's true, we don't touch each other. We just masturbate."

Marie carefully eyed both of us, but seemed satisfied with our answer. She believed us, and now the tension in the air between all of us could clear.

"Fine, I believe you." She paused. "We've all walked in on you enough times, Kevin. And Bree, I know how horny you can be."

I was appalled that she had ever caught me, since I never knew it. I wondered how many times she had seen me jerking off. God knows I had done it in enough places around the house, with people home even.

"So, what now?" Marie asked us. "I don't think it's fair to say that none of us can masturbate anymore, obviously. I can find other ways to...experiment, but I don't want it being awkward every time I go for a run, with you two knowing what I'll be doing as soon as I get home."

"It's not a big deal, Marie," Bree said. "We don't care if you masturbate. Hell, all of us do it."

"Sometimes together, I gather," Marie countered.

Bree's eyes seemed to light up suddenly, as if she had just had an epiphany.

"Hey!" she exclaimed. "Let's all do it together!"

For some reason, my eyes shot toward Marie and she was looking right back at me. We both blushed, and I was still rock hard in my shorts.

"I...don't think that's a good idea," Marie said.

"No, seriously!" Bree continued. "Marie, it feels sooo much better when you do it with other people. Imagine how good it would be after your run if we were all watching you, and doing it with you."

Marie actually seemed to ponder that thought. She did get off on the possibility of getting caught, which was really just a form of exhibitionism. And she could actually live that fantasy out by knowing we were watching her. As long as she wasn't put off by the incestuous overtones of all this. Bree was a horny little devil, so of course she didn't care. Marie was more mature and less spontaneous. It might be a stretch to-

"Ok, fine." Marie's simple statement caught me off guard.

"Yay!" Bree said, clapping her hands. "It'll be so much fun."

Now I wasn't hiding my erection anymore. I laid back as I processed what Marie was agreeing to, and ended up letting my tent out into their view. Marie's eyes widened, but she didn't say anything. Bree looked over at where she was staring, and just kept smiling.

"He has a really big cock, Marie," Bree said. "And he cums a lot."

Marie just stared at me, and I didn't move to cover myself up. Why? At this point, we were basically all going to see each other naked and at our most vulnerable. There was no reason to hide from each other now.

"I'll take your word on that last part," Marie said, "but I can see the first part for myself."

I smiled, feeling like that was her way of paying me a compliment.

"Can we do it right now?" Bree asked, practically peeling her clothes off already.

Marie glanced up, picturing Mom and Dad upstairs. "I guess we could. They won't hear us down here."

Bree was naked in seconds, and Marie slowly pulled at her pajama pants. I didn't want her to feel awkward, so I discarded my clothes like it was no big deal. She was watching me the whole time, and when my cock came into view, she finally got her pants off and sat on the couch with just her camisole on. Bree and I waited for her to finish stripping, and she blushed deep. But, she was never one to back down. So she pulled her top over her head and set it aside. Now all three of us were naked together. A few feet apart, and not touching anyone but ourselves. We weren't doing anything "wrong" at this point, we probably all told ourselves.

"Do you just..." Marie seemed to have a hard time getting comfortable.

"Just do whatever you normally do," Bree said, and spread her legs shamelessly. "We've seen you do it already, so it's no big deal."

It wasn't until I started stroking that Marie finally reached for her crotch. But she was still sitting cross-legged, hiding her goods from our view. Bree was quick to catch on.

"No hiding," she scolded. "It's more exciting when the other person can see everything. Don't be embarrassed. We know you have an awesome body, and that you shave."

Normally all of those little details might have made Marie more embarrassed, but in this setting they seemed to help. I figured Bree knew what she was doing, and just kept quiet while I stroked off. Marie nodded and leaned back, spreading her legs and showing us both her pussy. It looked really nice, and I could even see her little butthole too. She really did have a good body, lean and sexy. I stared at her pretty much the whole time, even though both of them were staring at me mostly. Still, I caught Bree eyeing Marie for some of the time, making me wonder if she was into girls even just a little.

The three of us eventually worked ourselves into a huffing circle of rapidly moving arms. Marie really took off on herself once we were all doing it. None of us were ashamed of our bodies, and weren't embarrassed that other people were watching us do our most private act. I loved seeing both my sisters stare at my penis with a look of desire in their eyes. This was great, and I kept up a nice medium pace so as not to blow too early.

Bree was the first one to pop. She cried out and thrust her hips up off the bean bag, rubbing her mound firmly in circles. It was really hot to see her cum, and even Marie must have thought so, because she grimaced and looked to be ready to go herself. I really wanted her to have fun this first time, so I quickened my own pace and hurried myself to the edge so she could watch me spew. I groaned loudly, so they both knew what was happening, and then started to fire off while they watched.

It was really hot to have just Bree watch me cum, but having them both was even better. My balls tightened and drew up beneath my shaft, and semen shot out of the tip and tagged my chest on the first shot. I painted lines across my torso, seven or eight of them, before dribbling out the last bit into my belly button. I enjoyed it immensely, but was sure to watch Marie as she rubbed at her cunt while she stared on at the show.

Finally, her eyes closed tightly and she made a really sexy grunting sound that I didn't remember from before when we spied on her. She whimpered a lot like Bree, and threw her head back as her orgasm tore through her. She reached up with her free hand and grasped her breast, which I thought was the sexiest thing I had ever seen before. When it was over, she looked positively glowing and satisfied. Bree was still happily rubbing as she watched, but she wasn't trying to cum again. She was just enjoying herself.

"Awesome!" Bree said when it was obvious Marie was finished. "How was it?"

Marie had to catch her breath for a moment. "It was really good, I admit. You were right, watching and being watched make it better."

"Better than the adrenalin?" Bree asked, smiling.

"I don't know, we'll have to try." Marie smiled, especially at me. I think she really got off on seeing a nice big cock explode.