...Ms. Collins, our headmistress.” you say awkwardly.
“Oh, so you like someone who is the head of our school, huh?” Your girlfriend states as she clambers on top of your dick.
As you begin thrusting her moans become lower and huskier, her hips widen pressing her now beautiful, heart shaped rear into your groin. Her stomach tightens into a firm six pack and her nipples enlarge and breasts swell out to a hefty F-cup. As your girlfriends face begins to pop and change shape, her brown hair becomes straight as a ruler and darkens into black while growing down to her waist and tying itself into a headbun. Your girlfriends formerly dainty round face has formed into a mature, yet sexy face with a mark on her left cheek near her eye. Finally slight muscles fill out her arms, back, and legs as barely noticeable wrinkles work their way into her skin.
Now your girlfriend is completely a woman who you calls her Ms. Collins, she shouts,”Keep it up, young man. Cum into me!!” Upon which you release your semen.
“Well, you lasted much longer than I ever thought, young man. What do you say we keep this continue when your parents get home?” Your shapeshifting girlfriend in the headmistress or principal's body says as she cuddles up next to you.
Picking up her role playing queue, “Hehe, I love when you say that, ma'am.” Grabbing her by the ass and pulling her in for a kiss.
“So, what would you want to do next?” She says, holding your face in her hands.