"Hey, babe. If you don't mind, could you turn into my mom so we can have some dirty incest fantasy?" you ask her as she smiles and really like the idea.
"Ooooohhhh, I like the sound of that, honey. Okay, if that what you ask, I'll do it." your shapeshifting girlfriend replies as she begins her transformation. You first saw her breasts(which were C cups) are growing into double F cups and so as her slim body shape into a beautiful hourglass figure, then her face and voice are changing into someone a mature and very beautiful of your mother's appearance. And finally in 10 seconds later, when her transformation was complete, the person who is on top of you isn't no longer your girlfriend, but the perfect naked body of a beautiful woman you just happen to call mom. And then, your 'mom' (who is your girlfriend morphs into) appear to have a sexy lingerie, she looks down to you with a beautiful smile. "Wow, you're really look like my mom, babe." you break the silence as you're amazed her.
"Teehee,... thank you, sweetie. I'm glad you're enjoying it, but please call me mom." your transformed girlfriend replies back as she want you to prefer her as your mom, it seems like her attitude is also like your mom which makes interesting.
"Yes, mommy. I understand." You answer as you understand about the situation. With that,, your girlfriend in your mother's form came closer you could not control yourself, but just erect your dick on her butt which she surprise. "Oh my, has my baby boy a hard one, I guess you're very horny for mommy."
"S...sorry, I couldn't help it. It just you're too sexy, mom." you reply.
"It's okay, sweetie. Mommy took care of it." your girlfriend/mom said as she leans her hand down to your cock and do a little handjob. "Mmmm... it seems like your little friend here is so hard and stiff, let's say we begins to make love, shall we sweetie?"
"Yes, mom... Can we..."