On her asshole!

"Let me blow between your glorious ass cheeks, Matron." I say, my nuts tensing. "Spread them so I can see my spunk dripping off your little star."

"What a naughty-minded boy," she says. "But you have done so well by me, that you shall have it."

Matron kneels upward, my throbbing pole sliding out of her dripping cunt, then she turns round and straddles my legs facing my feet. Grabbing my cock with one hand, she levers it between her buttocks and slides it up and down over her rear hole several times. She's already wet down her crack from her copious fuck juices. Then she kneels forward and spreads her big, perfectly-curved buttocks with one hand whilst the other hand blind-aims my cock tip at her ruddy, crinkled butthole. Matron strokes my hard shaft quickly as she awaits the pasting.

My breathing becomes shallow and ragged as the sensation in my balls rises while Matron's plump buttocks jiggle slightly with the pumping movement of her hand jerking me off at full steam ahead. My eyes fix on the perfect globes, the shadowy cleft, the ruddy star of her anus, the tip of my cock pointing...there! I let out a hiss as my cock shudders in Matron's skilled hand and erupts, blasting her deep butt crack with hot cum. An audible "splat! splat! splat!" sounds as I squirt thick gouts of pearl-white cream forcefully onto Matron's anus.

Matron’s hand continues to milk me, squeezing my shaft tightly at the base, then pulling upward, making the last vestiges of my cum dribble from the eye of my cock onto her hands, which she then wipes on my thighs, the rest of my sperm oozing down between her buttocks.

Matron turns and seats herself facing me on the bed. She gives my still-hard...well, my ever-hard cock an affectionate pat and says, "Well, Mr Doe, I certainly had fun, what about you?" She continues to pat me gently.

"Mmm, yes, the service towards.... patients' happiness is very.... commendable," I joke with her.

Changing the subject slightly, Matron comments. "I know it's technically an injury, your permanent erection, Mr Doe, but it really is quite amazing, it's still as hard as it was during our fuck, absolutely no wilting whatsoever has occurred. Its not even been a minute, but if I wanted to, I could fuck you again, and again after that." She then seems to go into a private train of thought, her hand not moving on my cock any longer.

I think she’s debating another round with me and my "old fella"...