My sister Karen is two years older than me. She was always quite promiscuous and I think she started having sex when she was fourteen or so. She is extemely outgoing and open sexually. She has always been a little chubby, and developed some nice full tits (a D-cup) and a shapely round ass around the time I was thirteen. She was very pretty and had a lot of boyfriends.
I on the other hand have always been very shy and quiet. I did not go out with a lot of girls and found sexual matters to be personal.
When she first started talking about sex, she noticed how uncomfortable it made me. She enjoyed that and would describe to me how to stroke a penis or give a blowjob, just to laugh about how I would react by covering my ears or screaming at her to stop.
Karen used to walk around the house in either her bra & panties, a towel or a nighty. She always left her bedroom door open. My room was directly across the hall, so sometimes I would glance in and see her getting dressed. I started to notice that her panties looked so soft and comfortable.
Needless to say, when she went out I went through her underwear drawer and would try on certain pairs while laying in her bed. Sometimes I would rub my dick around in her panties until it got hard, then jerk off to the thought of her walking in and catching me. I had never thought of her in that way before but somehow I realized that putting on her panties really turned me on. I was always careful not to have any 'accidents' inside her underwear and if I did, I washed them immediately. I also tried on her small cut-off shorts, tight skirts and many other tight items.
After I began this behaviour, I started to check Karen out a lot more while she pranced around the upstairs in her lack of clothing. Her big tits were beautiful. Sometimes she would wear really low cut tops and sit on the floor in my room and talk about stuff. I always seized the opportunity to stand up and look directly down her shirt at her beautiful big tits.
When I was 17, Karen walked into my room one night. She needed me to cover for her so she could lie to her boyfriend. When I refused to cooperate, she tried to convince me by using graphic sexual language. She said things like 'You know what Jimmy (her boyfriend at the time) likes? He loves it when I grab his dick through his pants and rub it.' This time, I just let her talk and pretended not to be effected. After about two or three minutes of listening to my sister describe a sex act I was rock hard.
Karen decided to turn up the heat a bit by taking off her shirt, exposing her bra with her plump tits popping out of the top. I also noticed she was wearing one of my favorite pairs of panties judging by the strap sticking out of the waistband of her skirt. I don't even think she was viewing it in much of a sexual manner, more to embarass me into submission. 'Don't make me take off my skirt,' she said. I decided to take a stand and challenged her to do so. In seconds, she had her skirt off and was sitting beside me on my bed in just her bra and panties. I had seen her getting dressed hundreds of times before but now she was right next to me.
I looked at her panties, the pair that I had worn just the day before. I could make out the shape of her pussylips through the soft tight fabric. I also noticed that the tops of her nipples were now peeking out of her bra. 'Still not uncomfortable enough?' Karen asked. 'Well fuck you cuz I aint gettin naked.' She left her clothes on the floor in my room and walked across the hall. I enjoyed the sight of watching her big ass shake as she walked away.
A few minutes later she returned wearing a new set of panties. 'Here!' she said, throwing her used panties an me. 'I know you like these ones, they're all stretched out, put them on.' My face turned deep red and Karen knew she had me. 'Put them on or I tell mommy and your friends that you are a fag!' I was in a bad place. I had always fantasized about her seeing me in her panties but now I didn't want to do it. I had a huge throbbing boner and was ashamed by the fact that she turned me on. 'Anything else' I pleaded. Karen insisted this was the only way she would keep her mouth shut. 'Go ahead, you love wearing womens clothes.' she said. After unsuccessfully denying the allegations, I relented and brought the panties with me to the bathroom so I could change. I knew she had seen a lot of dicks and she told me how big some of the guys were, so I didn't want her to see my penis.
I stripped naked then pulled the nylon panties up to my erection and jerked off in the sink to get it to go down. After I cleaned myself up and stuffed my now soft dick into the panties, I emerged from the bathroom and nervously stepped into my room where Karen was standing, still in her underwear waiting. At first she looked down at me and turned away, then looked back down and started laughing.'Oh my God, I'm sorry' she said,'Its not funny.' While laughing, her boobs were shaking around and I started to harden back up. Within a minute or so I was almost completely erect. My sister noticed and got an intrigued look on her face. 'So my tits get you excited, huh' Karen teased. 'Don't worry. I have that effect on a lot of guys. I am hot after all.'
I was speechless. 'And I'm still wearing my bra!' she exclaimed. 'I wonder what these would do?' At this Karen removed her bra and let her big titties drop free. My dick was now throbbing and dripping pre-cum. 'Take those off, you're gettin em all wet! Gross!' Karen knelt down in front of me and pulled down the panties, sending my dick flopping back and forth. I was now standing in my room completely naked with my sister in only a pair of panties.
To my surprise, Karen grabbed a hold of my dick and started stroking it. 'Shhhh..' she said 'I've done this thousands of times. Its no big deal.' I could tell. She started jerking me with her experienced hands, spitting on my cock and jerking with a twirl like a pornstar would do. She got me to cum in about a minute. When she felt me, Karen directed my dick at her tits and shot all over them.
Our relationship got a little weird after that, at least on my part. On one occasion I made sure to sleep in her bed when she was out so she could find me there in only her panties. As soon as she woke me up I got hard and took off her panties to give back to her, exposing myself. I then stood in her room and talked to her while I was naked with my boner poking straight out. She also made sure that I would catch flashes of her tits from time to time then grab my dick to see if it made her hard.