In the fitting room

 ... The classic ghost costume for me please." you said as the shop attendant handed you a package of the costume.

"That's so lame..." you girlfriend complained

"You may try this first if you like sir. Because there are a few sizes, and it'll look much better if you wear a size that suits your body type." she said as she directed you to the fitting room.

You find it funny  why just to try a plain white sheet you are asked to do it in the fitting room, it's not like you're going to take out your clothes anyway. But you complied and went into the fitting room.

You took the white sheet off the package and covered yourself in it, aligning your eye with the holes. But the sheet is actually way too short, since it was only covering up to your knee.

"This must be kid's size." you thought to yourself as you took off the sheet and going back ou to ask for the adult size. But before you can come out, you saw what looks like a belly dancer's bottom half of the costume were hanging behind the fitting room door probably left by the previous customer. 

As a random thought went through your head to try it on. So you slide your pants down, and wear the bottom. Immediately you felt tingling all over your body, and you watched as your body slowly shifted and becoming more and more feminine. Until you can barely recognize yourself in the mirror. You have turned into a beautiful girl.

You proceed to take off you shirt too, letting your newly developed breasts hang free on your chest. Then watching your feminine form, youbegan shaking your hips, making your bottom rattle.

"Is everything okay?" you girlfriend asked from outside

"Yeah!" you said realizing your voice has changed too. Your girlfriend was so confused of what happened since she was waiting in front of your fitting room as noone else walk in there. So you open the door, to show her your new form.

You shook your hips, making your bottom rattle and you can feel your new boobs jiggle folloing your body movement.

"It's me babe! What do you think?" you asked showing her your body, but your girlfriend was so shocked and speechless she just stood there watching what used to be her boyfriend now in the body of a woman, shaking her hips.

"Ah! I see you like our new body shifter costume sir, um- miss.. It's a bit more pricey compared to the usual costume we sell, but we can guarantee that you won't regret it. May I get you the top?" the shop attendant saw you inside the fitting room and you immediately nod asking her to bring you the complete set of the outfit..

Your girlfriend walked in the fitting room and touched your jiggling breasts as you moan softly feeling how sensitive your new nipples is. 

"I think I'm completely a woman now, this is insane. I'm totally getting this costume." you said to your girlfriend as she smiles thinking of what you two can explore after a night at the party.