It's clear you're very turned on by the sight of your own step-Mother's bare belly.
I'm sure there are all sorts of thoughts, feelings, and desires rushing through your body.
Tonight, after I return home from work, I run a bath for Myself, and then call you into the bathroom.
So, I thought, maybe I could let you pleasure yourself while you watch Me get wet in My sexy outfit, and in exchange, you pay all the rent.
Next thing you know they are getting naked and things get steamier.