Ask for something smaller

After putting it in and out a couple of times you push it inside her one last time.

"I think I got the hang of the movement now, but there is a bit of a problem..."

As you talk you take off the pants keeping the skirt, then you spread your cheeks to reveal your petite asshole.

"... my behind is very tight, I don't think I can fit that"

"Of course, you will need time to build up to this size. I usually start my clients with a relaxing massage to loosen some tension and then start with a small plug, that you should keep in 15 minute increments. Does that sound good to you?"

"Yeah, makes sense"

"For the massage you should stay on all fours with your ass up and your chest down"

You eagerly comply to the request, fully aware that in that position she can see how moist your pussy is. You very excited for your first anal experience, you feel that you are going to like it.

She puts her finger on your ass and starts massaging it lightly, you loosen your anus in response. You play a bit with her faking embarassment

"Ehm, I don't know, this feels like it's starting to get very intimate, are you sure this is not inappropriate?"

As you tell her this you subconsciously push your butt towards her, just enough to make her first knuckle enter your asshole. She notices your body language and calls your bluff

"You're right, maybe I got carried away seeing your body; if I'm making you uncomfortable I will stop"

Meanwhile she pushes one more knuckle in your ass, you resist the need to moan

"I wouldn't say uncomfortable, just surprised. I only want to make sure that this is purely professional"

Her finger is now making circles in your ass, the sensation is foreign but very pleasant.

"If you wanted to keep it purely professional you shouldn't have ripped a hole in your pants just to tease me"

Before you can reply she pushes a second finger in your ass, at this point you cannot resist and let out a lustful moan. It takes you a few seconds but you finally manage to respond