This is not to be the focused event, but rather a build up to it.

I'd like a focus on steps along the way: Her top taken off her, examining and toying with her body, the blowjob she gives you, peeling her panties off of her slender body and finally, insertion, and the finale -not withholding.

Feel free to look at past posts for more detailed ideas. She lines it up, holdnig it upright in her hand, lining it up and lets herself down. You: "Oh fuck you're so tight." She whimpered: "Are you sure about this?" You: "Just keep going."

Example:

She pushed herself down a little further. She felt your cock stiffen and flex.

Her: "Are you sure?" You: "Yeah... oh gosh.."

She froze, feeling it flex again, stiffening; flexing half inside her tight lips.

You: "Oh fuck.."

Her: "Are you going to cum?"

You: "I don't think so.. keep going..."

She pushed a little further.

You: "Okay, maybe."

Her: "Maybe?!"

You: "But don't stop. Go a little further."

Her: "Further?"

She pushed down a little further.

You: "Oh god..." Her: "What?!"

She felt your cock flex inside her. It started pulsing; throbbing.

You: "Oh fuck -AgH!

I am 18 and all participants and characters must be 18 and fully concentual; she might be confused by what's happening. For the sake of arguement, she'd agreed to the bets up until now, though impromptu and unplanned, unexpected on her part.