This was an idea I had and thought I'd share. Maybe someone will find inspiration.
It starts with a girl who is a bit of a tomboy. Very intelligent and well-behaved. Raised by her grandparents. She sort of ends up discovering her beauty because of her aunt's husband.
Her uncle has always been a loser. With women, with money, and in general. Now he is middle aged and overweight with the hair that isn't balding turning gray. Resentful toward women and everyone he feels has kept him from what he wants. She never understood why her aunt married him.
She eventually notices the way her uncle looks at her. Taking every opportunity to be around her and stare at her body. Thinking of the things he must be imagining about her. Those dirty thoughts and the feeling of being someones fantasy begin to turn her on. She even starts to tease him a little on purpose. Walking around in her panties while babysitting her cousins. Or leaving the bathroom door unlocked while taking a shower.
Her aunt ends up passing away. Her uncle seems genuinely distraught and she feels so bad for him. She tries to help out any way she can. He had planned a ski trip and suggests maybe she could come along. They could even leave a few days earlier and her cousins could meet them once school lets out. She doesn't want him to be alone and feels he is trying to thank her for her help. So she agrees to come along.
At the house her uncle rented he convinces her to drink a little with him. Then he tells her that the guy who owns the place does some photography. There is a camera setup and clothes. He suggests they have a little fun. She can be his model and take some pictures. She agrees. Of course the only clothes that fit her end up being overly sexy and even some lingerie. Not thinking completely clearly and enjoying teasing him she plays along. Things get really steamy.
When they head to bed he tells her he hadn't planned on needing an extra room so she'll have to share his. She declines and tries to sleep on the couch, but it gets so cold she is forced back into bed with him. Waking up she finds his large cock pressing into her from behind.
She is so worked up that when her uncle leaves to get some food she decides to touch herself. Calling out his name she doesn't realize he is standing there watching her. Once she notices he convinces her to keep going and let him watch. They end up masturbating together. After he convinces her to shower with him. This continues further until she ends up sleeping with him. Then they spend the rest of the trip as if she were his lover. Showing open affection and finding private moments, even risky ones, to satisfy their naughty desires.
After returning home she ends up finding the receipts for the trip. Along with the camera and clothing. She realizes they are all dated just before they left. Her uncle had planned this whole thing as an attempt to use her sympathy, guilt, and desires to seduce her.
I also had some thoughts of where it might go if anyone wants to use the idea.