My girlfriend at the time had let me know early on that while cupping and stroking her breasts were fine, and it was OK to caress her tummy, she wanted to draw the line there. The afternoon she decided she wanted me to undress her completely and lie on top of her (still no hands from the lower belly down) was a big step for both of us.
It wasn't until weeks later, after some petting in the car in a safe location (my family lived out in the country, and Mom and Dad had promised we'd always have privacy if we wanted to park on the long driveway leading to the house), that my girlfriend surprised me again by whispering, "Would you like me to take off my pants? You can touch me inside, if you want to."
My heart was pounding, but of course I said yes. I still remember hardly believing it when she unbuckled her belt, opened her jeans, then lifted up so she could pull them down, and her panties with them. She slid her legs out and let her pants drop to the floor, then reclined the seat, spread her legs, and guided my right hand between them. She was warm and wet, and after I stroked her a little, she smiled and guided my middle finger inside her.
I remember being surprised by the ridges, and the angle of her core, which made her giggle. "Not what you expected?"
When I put two fingers at her opening, she nodded, and they slid in easily. I fumbled around, trying to masturbate her, but she said, "Just exploring, for now.”
What was most thrilling for me wasn't the feeling around, per se... It was her opening herself to me in a way no one ever had, before, and a way she never had before, with anyone else.
That was as far as we went that night, but the scent of her on my fingers the next morning let me know it had really happened.