Step-Mommie's Lesson in Erections

I've been noticing that you're going through some changes lately, dear. It looks like your hormones are really throwing you for a loop, aren't they? I can see that you are worked up just talking to Step-Mommie, pitching a tent in your shorts like that! Apparently I need to teach you how to control those urges with some manual stimulation. Now, drop your trousers and show Step-Mommie how you've been developing. Oh my! You're going to need some spit to lube that thing up or you'll chafe in no time. You're going to wrap your hand around your cock like this...