Sophie doesn't want to stop, but she's modest

"I don't want them to see," she whispers, "but if you want to reach into my shirt and feel, you can."

The words are barely out of her mouth before you are instinctively reaching for her breasts. You feel their smooth warmth just as her friends gasp in surprise. Your hands cup over her breasts and you squeeze them, feeling the sensation of flesh in your hand, marveling it in. The sensation of your cock in your hand is immediately forgotten.

"God, you feel so good," you whisper.

Looking over her shoulder, you see the class enthralled by the sight of your cock. You look down to your cock and see that it's completely hard, standing straight up and throbbing. You gasp, realizing with surprise how delightful it felt to touch her rather than yourself.

Diana obviously sees how aroused you are, and is explaining to the class what's going on. You are so excited by the feel of Sophia's breasts that you forget to listen. All you can do is knead her breasts and squeeze her nipples between your fingers as you feel your cock harden beyond belief.

Diana comes are beside you and whispers in your ear, "Joe, I know we are friends, but I'd like to demonstrate to them how the male body responds when the penis is touched. Is it ok if I stroke you as you play with Sophia's breasts?"