Chapter 1
"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?"