I believe it is the combination of penetration, g-spot and just getting close enough to touch … but not touch it …..
personal share:
I will never forget my first time. :) It was on bunk bed and when we were done and she came really hard … she goes well I am going to be sore for a while and had blood.
I said .. oh you were a virgin too and she chuckled and said no honey you were just too big for me and then blushed.
There was no sex for a few days after and we were very cuddly and her friends said what is up …. and she blushed again.
As I have shared I have a horse farm, and have helped with the birthing process, so it amazes me how strong and powerful the vagina is.
So when we binged through the Magician’s when Queen Margo said Grow a Vagina boy or lady tits up … I chuckled because she was right ….
One of my ex’s was a size queen …. while I had friends far larger then me, well I always believed in the use of toys …. she would shudder sometimes as she said wait that isn’t you …. and I whispered I know … just wait I am coming to join it ….. soon … (then I would click the vibrator on).