She morphs into your aunt.

As your girlfriend/mother turns her back, you hear a loud crack and the slurping and shifting of her transformation.

You see her skin become slightly tighter and smoother, her hips round out and her ass becomes tight and smooth. Her height reduces significantly and her long hair pulls into a short bob. As the sounds and moans subside your girlfriend turns to reveal the form of your mother’s much younger sister, your Aunt.

Her breasts are smaller, but rounder and perkier. Her face is younger but still familiar. You can spot tight muscles through her still rather matronly form and your dick is still at attention.

“Ah it feels good to shed some of that mass. Why don’t you say hello to your 'auntie'?” The petite MILF before you asks as she crawls over your bed to begin to make out with you.

She works her way down your torso eventually nestling your dick between her ripe round breasts and soon sucking on it with her full lips.

You finally penetrate your ‘Aunt’ and release a wave of semen into her. She pulls away, her vagina dripping as well before cuddiling with you to ask, “so what now sweetie?”