My name is Adam and I'm 15. I live with my mom and my sister Emily who's 13.

This story is about the other morning. My mom had left early to apply for a new job since she hates her waitressing job and Emily and I were getting ready for school. Emily was in the shower and I was finishing breakfast waiting for her to be done with the bathroom (we live in a small house).

Anyway, I heard the shower stop so I headed up stairs figuring she was almost done. I grabbed a towel and knocked on the door.

"C'mon Em I need to shower too."

"I'll be out in a sec, jeez." she replied.

I stood there for a second or two then she opened the door. I was caught by surprise since she was just in her towel and her hair was still soaking wet. She has fairly long hair and something about her being soaking wet got me excited right away. The towel was wrapped around her just barely covering her boobs. Now, she has kind of small boobs but there was still a little cleavage and there was droplets of water on her shoulders and chest. I must have been kinda staring at her in shock because she said "Well move so I can get by." and then she brushed past me. I don't think she noticed that my boxers were bulging a little at the sight of her. I watched her walk to her room. The bottom of the towel barely covered her tight little bum and her glistening legs looked really sexy too.

I cleared my head and went into the bathroom. I started the shower, tossed off my boxers and stepped in. I was still thinking about how hot my little sister looked and was kind of surprised at how turned on I was. I started stroking my cock and closed my eyes to picture her. In my mind I imagined her towel slipping down and exposing her small but firm boobs. I was getting really excited about this little mini fantasy when she knocked on the door.

The knocking snapped me back to reality just as she opened the door and walked in. The shower curtain wasn't completely closed so I turned a bit to make sure she didn't see me.

"I need to dry my hair." she said casually. I didn't mind really but it was definitely the first time she'd ever come into the bathroom while I was showering.

Well, the only thing I did mind was that I was getting pretty close to a nice release before she knocked and enjoying my fantasy. Anyway, I resumed my usual shower routine and heard her flip on the hair dryer. I peeked around the curtain and saw that she had put on a t-shirt but her legs were still bare. The shirt came down to the middle of her bum but I couldn't tell if she had panties on or not (well, not without totally bending down which would have been kinda obvious). She had used the blow dryer to clear part of the mirror but was at a bit of an angle so she couldn't see me in it. I looked her over while she was focused on drying her hair. There was my 13 year old little sister. 5 foot 2, blonde hair, long legs for her height and small but pert little boobs. Her t-shirt was a bit wet (she must have thrown it on before drying off) and clinging to her a bit.

My cock throbbed again as I looked her over as if to say "keep stroking". I was about to resist that urge and get back to my shower (maybe turning the water a bit colder) when she did something incredible. She bent over and let her hair drop down as she continued to blow dry it. She was using one hand to hold the hair dryer and the other to brush her hair while she dried it. Not only did this mean she wasn't looking in the mirror any more - removing even the small chance she might see me peeking at her - but while bent over like that her shirt was pulled way up so that her gorgeous tiny little tush was pointing right at me. What's more is that my sweet, little sister was wearing thong panties! I couldn't believe my eyes. I have always thought of her as so cute and innocent (well, she does make jokes some times about sex but nothing crazy) and here she was wearing sexy panties. They were baby blue with darker blue stripes. The way she was bent over, with her legs slightly spread, I could see the little mound where her perfect little pussy would be. My hardon got harder than I've ever known as I stared at my little sisters ass and pussy just a few feet in front of me!

I was stroking faster now, careful not to breathe too heavy or make any other noise. I was getting close to cumming again and was trying to decide if I dared risk cumming with her right there. I decided that between the noise of the hair dryer and the shower that there was little risk involved so I renewed my focus. I imagined how it would feel to be touching that pert little tush. To run my hands along her long slender legs. To press my hand against her panties and feel the soft pussy beneath the fabric. I imagined her pushing back against my hand, grinding her pussy against my fingers. The wetness coming through the cotton of her thong panties.... then I had the most incredible orgasm I've ever had. I nearly lost my balance in the shower.

By the time I regained my balance and had sort of cleaned up a bit she was back to standing and finishing off her hair. She snapped off the blow dryer and walked out of the bathroom back to her room. I took a moment to imagine her stripping off her t-shirt and standing there in just her panties as she decided what to wear. I shook my head to get a hold of myself (I had no time for another fantasy) and turned off the shower to go get dressed myself.