so, for me one particular instance was when my gf at the time was leaning over me while we were both sitting in bed. she gave me a bj and through mere proximity my foot started caressing here private parts. one thing led to another and while she continued eventually my big toe slid inside of her.

it was after she'd cum when she looked at me with this hard to describe mixture of horniness, post-nut-clarity and shame that i figured sex for me is more than just pleasuring one another