trying to find a story

I'm trying to find a story I started to read a long time ago but I can't find it. It starts off with this kid in a shop (whether it was a family shop or a random shop I can't remember) and when he picks up this necklace and sword he ends up getting transported to another world as a she, I remember some properties of the necklace that allowed it to adapt to what ever outfit she wore. And something about Iron wolves being similar to zoids. but thats all I got. If you could help me that'd be great.