This happened whilst I was working away from home. I was staying with relatives, my niece Alison and her parents. Alison is twenty years old at the time of writing this but was eighteen when the following occurred. She is five feet tall with large tits, difficult to estimate the size of them but they are prominent because of her slim build.
Her face is plain but her total appearance makes her attractive. At eighteen I got the feeling that she was not sexually experienced and was almost certainly a virgin.
Now for the story.
Most nights I would stay up with Alison. Her parents would generally go to bed early leaving us alone. We talked and watched TV. After the first few days we settled into a routine. I would sit on the settee and she would sit opposite on a large armchair covering her legs with a blanket. After a few minutes of watching TV she would discretely slip her right hand under the blanket. I would pretend not to notice. I could not see much, her legs were covered. However I could see the movement of her hand as she fingered herself. Sometimes when she started she seemed to struggle to get her hand in so I assumed she had her fingers inside her knickers rather than just rubbing on the outside. All the time we would talk and watch TV and I would continue to pretend that nothing was happening. This would go on for about thirty minutes. She would then pull her hand out, say goodnight, and go to bed. A few minutes later I would also go to bed. My bedroom is next to hers so quite often I would hear her finish herself off. She is very loud, especially when she comes. Fortunately her parents could not hear as their bedroom is one floor above and on the other side of the house.
After a few weeks this changed. One day she came home very late from school after a netball match. Her parents were already in bed. As usual she sat down on the armchair, but the blanket was gone. She looked around for something else then decided to just use one of the cushions from the chair. Her hand went under the cushion and she spread her legs a bit. The cushion was small and her school skirt was short so this time I could see a lot of leg. She talked about the match, she was excited because they had won. We then got back to watching the TV. After a few minutes I noticed she had closed her eyes and that her legs were spread quite wide. I moved a bit so I could get a better view. The cushion was not covering a lot. I could see her white knickers with two fingers inside. She was rubbing herself.