A month has passed since your girlfriend revealed to you that she had become a shapeshifter. That day you told her that you would only keep her secret if she taught you to be a shapeshifter too. She readily agreed to be your teacher. Since then you have been going to her house every night, telling her parents that it was just to study, and she has been teaching you.
In the first days it was complicated and you were unable to make any changes, managing to do some things almost a week later when, despite not being your intention, you changed the color of your hair leaving it purple. You had to spend a whole day with your hair in this color telling others that you had dyed your hair to pay a bet that you had lost.
In the following days you learned how it works, making changes more and more easily. With a month of learning you can still make relatively small changes, like turning one small part of your body into another, sometimes changing something a little bigger with some difficulty. All of this recalling the warning that your girlfriend had given saying "Keep in mind that you must remember your original form very well, otherwise you will be unable to return to normal."
There was a night when you were alone at her house again. You and she were looking out the bedroom window until her parents' car turned the corner and disappeared from view, right after that your girlfriend took off your clothes and told you to do the same.
"I've been teaching you how to transform for weeks now, so today I'm going to test to see if you're ready to advance to the next level." your girlfriend said
"And how will this test be?" you asked
"Simple, we're going to have sex and I'm going to change in the meantime. I want you to change your body according to what I do. Understood?" she said. You gave her a thumbs up and she hugged you and kissed you.
Did you realize that the test had already started when you realized that your girlfriend was making the move that she wanted to grab something right in front of your chest, understanding what she wanted you made a pair of D-cup breasts grow on you, which she grabbed immediately. You got a hard cock and soon sat something wet covering it up and looking down you saw that your girlfriend had turned her pussy into a mouth and was sucking your dick, but leaving space that you filled by increasing the size of your dick.
"You're doing well, let's increase the difficulty a little now." your girlfriend said and immediately afterwards her mouth disappeared completely, the area then stretched and the skin at the end opened, completing the 9 inch hard cock that had formed in her face, as well as the balls that formed on her chin. You then turned your mouth into a pussy, with which you received her facial cock with great pleasure. Your girlfriend pulled you closer and guided your hand to her ass, you then turned your index finger into a dick and placed it in her ass.
It was your first time having sex with your girlfriend with the two of you transformed, so you couldn't hold on too long and soon came in her mouth and ass. You could feel the pussy on your face contracting around her cock while you came, even though she didn't stop fucking you, instead she increased the pace and quickly came.
Once finished, your girlfriend looked at you hard with her now soft cock dangling just above her breasts. She said with the mouth between her legs "You did well in this test, it still wasn't perfect, because even changing the parts of your body you still haven't changed your functions correctly, otherwise you would have choked on this form since you shouldn't be able to breathe through the vagina in your face. Despite that you did well."
"I figured I was forgetting something but I didn't know what, I just thought about changing it sternly and forgot about the inside." you said
"Don't worry, you'll get used to it. Now I believe that we can move to the next level, until now you have only learned to transform an existing body part into another one, from now on you will learn to create new parts for your body like this." your girlfriend said growing a new arm under her right arm.
You tried to do the same, but only managed to make a lump appear that resembled a breast without a nipple. "Really, this is more difficult." you said
What's nex?t