Let's do this.

You approach your friend as she leans back against the chair. She looks at you almost hungrily, her cheeks flushed, her chest heaving. You can see the blush in her upper chest, in area revealed by the single button she has unbuttoned below her collar. You glance down and notice a clear wet spot on her panties.

As you draw nearer she takes a couple steps over to the desk, slides her panties swiftly to the floor, and sits herself on the edge of the desk. She's not exactly spreading her legs for you, but she's clearly ready to, as she watches you with a half-smile. Whatever nervousness she might have had a moment ago seems long gone.

Once you're within reach, she turns to the class while simultaneously reaching out and grabbing your rock-hard cock. You feel a shock of pleasure as she grips it firmly and slowly pumps it up and down.

"Ok, we're about to have intercourse. I invite all of you to scoot in so you can get a good view. You'll want to watch to see how penetration works, and I want you all to be ready to see what a male orgasm looks like."

"Do you want me to pull out before I cum?" You ask.

Her thumb flicks across the base of your cockhead. She looks up at you. "I want you to come inside me, but for the sake of the class, yes, you should pull out so they can see you orgasm. Now...fuck me already."

As the girls gather around, you step in, following the firm but exquisite guidance of Diana's hand. As you move in, she sinuously wraps her legs around you, a warm embrace as you slide your cock into the wet folds of her pussy. She gasps as you enter her, then squeezes you with her legs, holding you against her. She looks up at you with a smile.

"Well, this isn't so bad, is it," she says slyly. You answer with a thrust, pushing even deeper into her. She squeaks happily, then nods for you to continue.

You begin thrusting, slowly it first, barely even sliding out of her, just in, in, in, as she squeezes you tighter and tighter. Every time time you thrust her mouth slowly opens wider and wider, short breaths coming out, sometimes as gasps, sometimes little vocalizations. She seems oblivious to the girls around you and aside from noticing that a couple of them are continuing to touch themselves with some fervor as they watch you, you're fairly oblivious as well.

You grab her ass for leverage as you speed up, your excitement building. She's starting to moan now- but she keeps stopping herself, maybe trying for some semblance of professionalism in front of her students. She moans, the squeaks and bites her lip as she cuts herself off. Then she moans again, louder.

Your other hand reaches up and starts to massage her breast over her blouse. She moans over louder, then leans in and gently bites your shoulder, trying to muffle her sounds. It's not working. Her cries of pleasure get louder and louder, and before you blow your load she loses it completely: Screaming her ecstasy into your chest, grinding her clit against you, squeezing you harder with her legs than you thought was possible.

Eventually she subsides. Her back is hot, and you can see her neck glistening with sweat. She's obviously out of breath. You hold her for a long moment as she collects herself- your cock still hard and quite close to orgasming but not quite past the point of no return yet.

Finally she looks up at you, her eyes shining, her face transformed. "That was amazing," she says, looking at you with with blissful delight, "You haven't orgasmed yet?"

"Nope," you say, "Waiting for you."

"Well thanks," she says with a warm smile, "But now it's your turn. Do you want to keep fucking me, or shall I finish you off with my mouth?"