This RP would be about a shy girl being released from her shell. She is bright and well raised, but painfully shy. To her bitter dismay, she is perceived as sweet and innocent girl, while inside she feels like a cheap fraud. She thinks her favorite (and only slightly perverted) fantasies reveal her to be a common slut.
So she is delighted when someone finally sees past her facade, penetrates her shallow defenses, and allows her to express some of the things she has long repressed. He makes it all so easy for her. Every day he creates opportunities to explore new facets of her sexuality. Each deed naughtier than the last. Each building her confidence and self esteem.
It is a slippery slope, and he makes it all seem so natural and totally acceptable. She soon discovers it is not a particular thing she enjoys, but rather the act of surrendering her innocence that thrills her.
The actual character roles can take many forms, but I prefer the more traditional. Perhaps stepfather/daughter, teacher/student, or doctor/patient. Let me know what interests you.
I am open to different interpretations of this scenario.