"...my little sister."
Your girlfriend gives you a weird look and says "I thought you didn't have a little sister. You're an only child right?" You start to laugh as you respond, "Yeah, I know. I just wanted to see the look on your face. I was expecting more shock, but I guess that will do. Okay, now for your real change, I choose....." You suddenly fall silent as you look at your girlfriend. "You choose what? Is there something wrong?" Your unable to say anything, so you point to a mirror. Your girlfriend sighs and looks into the mirror still thinking your joking around. When she did look though, she saw just what you did. She was changing.
The first thing she notice was that her short blonde hair had turned brown and grew down to a little past her shoulders. Next she lost about two inches in height and a couple inches from her waist and hips. After the body adjustments, her skin got a light tan and her nipples changed from a light pink to a medium brown. Finally her face seem to grow younger and began to resemble your mom's features more than her own.
When the changes finished, your girlfriend turned back to you, looking a little angry. "Hey, I thought you said you didn't have a little sister. Who the heck am I if you don't have a sister?" The strange truth was that you did NOT have a little sister. However, looking at her more and more, you had to admit that if you had a sister about the age of 15, this is what you would imagine she would look like. "Uh" you began, trying to come up with an explanation. "Maybe the room changed you into what my little sister would have looked like if I had one. You know, it might have tried to predict what she looked like, and that's who you are now. You are the little sister I never had."
Your girlfriend, still a little angry, let her expression loosen into a thinking look. She had to admit that your explanation did make sense, but she still thought of this as your fault. "Well, I may not like the situation, but I guess we'll just have to face the fact that you wasted your change for today." "Hey" you tried to protest, but your girlfriend just laughed. You knew she was playing back with you now, and decided to go with it. "So, I guess your going to be a brat like all little sisters I hear about. Well I guess I'll just have to punish you." With that, you began to chase her around the room.
While chasing her, you had to take note in how fun this was actually turning out to be. Sure this may not have been what you had in mind, but why not enjoy it? But after you had finished this thought, you finally caught your girlfriend and pinned her on the bed. With her pinned, you start tickling her as she giggles and pleas for you to stop. You laugh as you keep tickling her, but your tickling moves up her body, more toward her breast a navel. It's at this point you begin to feel a little awkward. Sure it's your girlfriend, but for a second it really felt like you were doing something dirty with a relative.
Your girlfriend sees you stop and tries her hand at an attack. She reaches an arm up and pulls you by your shirt into a kiss. As you two kiss, things begin to feel really weird. On one hand you know it's your girlfriend, but on the other it really feels like your kissing your sister. After the kiss you both slowly move away, and remain silent for a minute. However, after a time your girlfriend finally decides to break the silence. "So, did you feel like you were kiss your sister? To me if felt like I was kissing my older brother. This all is really strange. First I turn into a sister you've never had, and now I every time I want to do something with you it feels like....incest."
It was true for you too. Sure you may have never had a little sister or any other brothers or sisters, but what you saw when you looked at her was your little sister. What you felt when kissing her really did feel like incest. This was a very weird situation indeed.