A quick anatomy lesson

Diana walks over to you, smiling at the situation as she motions for you to stop touching yourself. Sophia puts her pants on her lap for warmth but leaves her shirt unbuttoned. You sneak a couple more peaks at the curves of her breast, and notice her noticing you look each time. She seems pleased.

"I'd like to show you all some of the basic features of Joe's penis." Diana says.

You chuckle to yourself, it's like you're a car at a car show!

She continues, "Joe, is it okay if I touch you while I talk? Class, Joe and I are actually friends outside of class, so this is a little unusual as far as situations go. Joe, it's totally ok for you to say no, I'd understand. But in past classes I often touch the models to demonstrate before letting the girls do it."

Your intensely hot friend is asking you if she can touch your dick in front of a bunch of pretty girls. Um, yes please. You play it cool. "Yeah, totally, whatever you need to do."

"Thanks Joe. So, class, this is the shaft of his penis." She stands next to you, and reaches down, wrapping her hand around your hard cock, holding it in a loose grip. You have to use your will power not to thrust into her hand. "Thanks to Sophia, he's already nice and hard. Can anyone tell me why his penis is hard?"

The blonde in the front row instantly raises her hand.

"Grace?" Diana calls, her hand still wrapped around you. You can smell her shampoo from this distance, she's only inches away.

"It's hard so he can penetrate a woman's vagina," Grace says.

"Correct," Diana says, "So, if he's inside a women's vagina, and he stays hard by moving in and out, then what would I do right now if I wanted to keep him hard?"

Grace's hand shoots up again, breast bouncing lightly with the movement.

"Someone besides Grace?" Diana asks.

Sophia raises her hand tentatively, and as she does so her unbuttoned shirt falls open, exposing far more belly and breast than you'd seen previously. There's even the quickest flash of a nipple, and you find yourself even harder than before, your breath taken away by the sight of her tiny, perfect breasts.

"Sophia?" Diana calls, "What would I do with my hand?"

"You'd pretend it was a vagina, right?" Sophia asks lowering her hand, to your disappointment, "Grip his penis and then slide your hand up and down?"

"Let's try it and see what happens," Diana says playfully. She increases her grip on your cock and starts slowly sliding it up and down. You gasp and this time you do push yourself into her hand. You look down and see the head of your cock appearing and disappearing and she slowly pumps you. She speaks under her breath to you, "Are you sure this is ok, Joe?" You nod assertively.

After a few timeless moments, she lightens her grip and slows her pumping. "It looks like you were right, Sophia. He's extremely hard right now."