Link

 .. Link costume" you made your decision and headed to checkout.

Arriving home you two were in a hurry to get ready before the party. As your girlfriend were taking a shower, you open the costume you just bought and decide to put it on.

"It feels like a girl's costume, this looks like a dress.." you thought to yourself, but quickly brushed that thought off and began dressing up. And as soon as you put the entire costume on, your suspicion were confirmed, it was really a link costume for girl. 

But then when you tried to take them off, your body has started shifting. Your figure become smaller and dainty, you shrink as you skin become smoother, you can feel a small bump was formed on your chest, as your penis is replaced with a soft and sensitive vagina. 

Looking at your new form in the full body mirror really shocked you, you look like a little girl. You felt your heart sank by the transformation, as your hormones started to affect your emotion. You began sobbing.

When your girlfriend came out of the shower and found a girl in link costume sob, she immediately rushed towards you.

"Babe? is that you? why are you a girl?" she asked but you stayed quiet unable to say a word. She then pulled you and embrace you in her hug. You can feel how small you are now compared to your old body as your girlfriend hugged you.

"I'm sorry, I should've told you that some of the costumes sold there has magic spell sewn into it to make the costume be more fitting and realistic, so I guess you just picked up one of them. And unfortunately the spell might be permanent if applied to the opposite gender. But don't be sad, you look pretty and cute." she said lifting your head as she wiped your tears.

"I can't be a girl. I don't wanna be a girl" you said in high pitched girly voice.

"I'm sorry babe, but that's what your life is from now on. Cheer up, I promise you being a girl isn't that horrible. I can teach you." she said giving you a soft kiss.

"Will this mean I'm no longer your boyfriend? Well, I know you're not a lesbian"

"Yes, but even better, you can be my little sister. What do you think, sis?" she said and a smile formed on your girly face.

"Now wipe your tears, put on your cute smile, and we'll have the best halloween party for tonight. And for tomorrow, I'll take you shopping."