Back when I was a teenager, during one particular summer vacation my younger sister went away to a camp and was gone for maybe a month and a half. She is three years younger than me, and for some reason that year she wanted to go away for a little while. It was pretty weird not having her around, but from the letters she sent she made it sound like she was having fun. I think it was the middle of July when the camp ended, and when we went to go pick her up she looked pretty different; her hair was bleached out from the sun and she had a nice, deep tan. That night we all went out for ice cream and just spent time as a family.
The next morning our parents had to work and, as usual I woke up pretty early. I had already eaten breakfast and was sitting out on the deck when I heard some dishes clanging around, so I went back inside to see how she was doing. I really wasn't expecting what I saw, but there was my little sister, standing with the refrigerator door open completely naked. Not only that, there wasn't a tan line to be found. She heard me and turned around and simply said 'good morning'. I just looked at her and said 'good morning...why are you naked?' 'We went naked all the time at camp, I guess I just got used to it.' 'I guess so, no tan lines?' She looked down and just laughed, 'nah, we all got a lot of sun.' I just shook my head when I walked past her, still not wrapping my head around my little sis being a nudist.
Later on that day I was sitting on the couch, listening to the radio and reading a magazine when she came and sat next to me, still naked. She was quiet for a few seconds until she said 'have you ever had the urge to just strip off all your clothes and run around the house completely free?' I just looked at her and smirked and said 'no...not really...' 'How come? You really don't know what you're missing, it's soooo comfy.' I just kept smiling and shaking my head and told her 'no, I'm not getting naked in front of you.' We just kept smiling at each other for a few seconds until she reached for my shirt and I had to slap her hand away. She did this a few times and I kept slapping, but then she lunged at me and we were wrestling around on the couch, laughing like crazy and me holding onto my clothes while trying to push her off. I held her off until I lost my balance and rolled onto the floor, and before I could get back up she jumped on my back and started pulling at the waistband at my shorts. I couldn't stop laughing and shrieking, but eventually I lost my grip, and even though I was kicking my legs, she got my shorts and panties off and threw them across the room, leaving me naked from the waist down. She jumped off me and crawled up by my head and just smiled, so I sat up and pulled off my shirt, leaving me as nude as her. I sat back with my legs out in front of me and my arms spread apart, and I asked her 'there, happy now?' She jumped back at me but this time put her arms around me and told me she loved me, and I just said I loved her too. She got up and said she was going to go up and take a nap, and before she went upstairs she grabbed my clothes and ran off with them.
About an hour went by and I was laying on the couch with my magazine, and she was right, it felt pretty darn nice lounging around with no clothes on. I would stretch out and spread my legs, loving the fact that nothing was restricting me. I closed my eyes for a minute and was just about out when I heard her making noise upstairs. It sounded different so I jumped up and ran to her room to make sure she was OK. When I got to her door I saw her laying on her bed, feet in the air, hand furiously rubbing her vagina. I just stood there in shock for a minute until she groaned loudly and clamped down on her hand, rolling over and seeing me. She didn't even seem embarrassed, she just laughed and said 'hey'. I leaned against her door and asked her 'so, I guess you learned how to masturbate at camp too?' 'Yeah, there was a girl there that did it in bed every night and she showed us how, after that we did it a lot. How often do you do it?' That question kind of shocked me. 'What? I don't know...' 'Did you this morning or last night?' 'No I didn't...why are you asking?' 'I dunno...I figured it was something we both did and could share with each other, I'm getting older, you know.' 'I know, I know...OK, maybe...twice a week.' 'Really? Sometimes we all did it twice a day, sometimes more.' 'We all? You all did it together?' 'Well...10 of us were in one cabin so we didn't have any privacy, so...yeah!' I couldn't believe all the things I learned about my sister that day, the baby of the family, but I also couldn't believe how horny I was getting hearing about it.
I just stood there speechless for a few seconds until I told her 'um...I really gotta masturbate now after hearing all that' with a laugh. I started to walk away and she told me I could do it there. 'Here? In front of you?' 'Sure, I can go again' as she started rubbing herself a second time. I just shook my head and said I couldn't believe I was doing this, but squatted down a little and started fingering myself. I was so wet my fingers were coated with my juices almost immediately, and I could only last a couple minutes before I felt my orgasm about to hit me. I bit my lip and fingered as fast as I could, and my orgasm ripped through me like never before, and I fell backwards not being able to let go of myself, rubbing and squeezing my clit until I came a second time. I was covered in sweat and I was covered with my own cum. When I sat up she was looking at me, and all she could say was 'that was awesome!' I just smiled and told her I needed to clean up, and even though my legs were wobbly I made it to the bathroom and wiped myself off.
Later on that day I was laying on my bed when she said she was bored and asked me if we could go somewhere, so I told her I could take her to the mall. We got dressed and I drove us there, and I bought us a couple cd's and some new sandals, and just spent the day as sisters. Sisters that no one else knew just masturbated together. It was kind of fun, standing next to someone or at a counter, acting normal but thinking 'you don't know it, but I just masturbated twice!'
That day started the rest of a summer of nudity and masturbation with each other, as long as our mom and dad weren't home.