You are a chair.
An overstuffed wooden chair, given sentience by an attractive young witch.
Being her favorite chair you enjoy her sitting her toned butt on you every time she has a dinner, reads a book, mixes potions, etc.
One day, your mistress returns home with a bunch of books.
After having a dinner, she sits down with a cup of tea and starts reading one of them.
A few minutes pass and you notice that your mistress is uneasy. She usually sits still while reading spellbooks or history books, but as she goes through this "Princess's Boudoir" book she starts to fidget around.
Her face grows increasingly red, and she starts to rub her thighs together. Eventually, you feel her panties getting wet.
"Are you feeling unwell, my mistress?" you ask, concerned.
"Hyaa!" the witch jumps off of you in surprise, dropping the book. "Khm, I am fine."
She looks at you and notices a small stain.
"Oh, sorry, I soiled you."
Your mistress takes the handkerchief and you feel her gentle hand rubbing on you as she tries to clean you.
"Do not worry about this. More importantly, is there something I can do to alleviate your discomfort?" you say, as you can feel her body heat being higher than usual.
"What? Ah, no... well..." she thinks to herself for a moment "If you don't mind?"
"Anything for my mistress." you answer enthusiastically.
The witch picks up the book and sits her cute little butt on you once again, your stuffing gently cushion her soft cheeks.
"Okay, then just... well... rub between my legs." she says, as she continues reading the book.
You reach your upholstery and trace along her damp satin panties, which makes her quiver and make a strange noise.
"Did I hurt you, my mistress?"
"No, it's a normal reaction. Just keep going." your witch starts panting heavily.
With your armrests, you embrace your mistress by her slender waist to prevent her from sliding off and continue caressing her crotch with your velvet upholstery.
The witch starts to squirm, dropping the book as she grasps at your backrest, overcome by pleasure.