Since getting married I constantly masturbate about my sister-in-law. She is very sexy girl and when my wife and I am around her she wears very revealing clothes. I seem to always get a good view. She has told my wife that she sometimes has erotic thoughts about me and I get the impression that she masturbates about these thoughts. This drives me wild. Last summer I was drying off after a shower and the bathroom door was slightly open. She is very curious and walked by the door when she realized it was open. When I saw her coming I dropped my towel and she saw everything but I pretended I did not know she saw me.
Now when I stay at her house I go into the bathroom and go through her panty drawer. I often try on her panties or swim suit as I rub myself. Sometimes a freshly worn pair of panties are in the hamper and I smell them adding to the fantasy. While I stroke myself I think about her touching herself while thinking about me. Wondering what she fantasizes about. The thought of one of us walking in on the other as we are about to cum puts me over the top and I blow my load. When I am done I make sure to place the panties exactly as they were so I am not discovered.
I hope that in the future I am writing a story about us masturbating while the other watches or each other.