F4TF #9 - First Times

The "loss" of virginity is commonly held to be the first time that you had penetrative sex with someone. This, however, is just one of a range of sexual "firsts" that we have and, quite likely, wasn't even the first of those "firsts". So, today we are asking:

What was the first overtly sexual act you performed on someone else or had performed on you?

How did you feel about it afterwards?