There’s two types of profiles for Mochifitter

The first and most common is the “Forward”/Target profile 順方向 This converts outfits TO that avatar with their profile. If you are trying to get clothes to fit your avatar, this is the conversion profile you need to get/create

The second and less common is the Reverse/Inverse/Source profile 逆方向 This converts outfits FROM that avatar to another avatar. If you have an outfit from this avatar that you want to fit to another avatar, this is the conversion profile you need to get/create

A reverse mochifitter profile (B) converts the costume to the template (Middle). A forward mochifitter profile (A) converts to the avatar from the template. (img from https://signyamo.blog/mochi_fitter/)

You’ll need to get both in order to convert outfits from one avatar to another.