Dryad

You look up and see a naked woman seemingly step from a tree. Even in the half-light you can see that her skin is a deep mahogany brown and her hair is a lush dark green. She looks down at you prone form and the vines loosen a allowing you to close your legs to a less painful position. They continue to stimulate your clit however.

The woman kneels down between your legs and reaches up to remove your bra. "I apologise if they hurt you" she says "They aren't all that familiar with human anatomy. Then again neither am I, not with female anatomy anyway. That is why I asked them to capture you."

"W-What do you mean?" You stammer.

"I need to study you so I can look and act more human. The fact is I'm the last of my kind in this area and so I can't find any of my own kind to fertilize me. I am therefore going to try to use a human male, but in order to do that I need to understand the human female reproductive system and the correct things to do to achieve fertilization. You will help me to do this…"