>>371072661
booth.pm, search kyoko or 京狐 under https://booth.pm/en/browse/3D%20Character%20Attachments and you'll find them eventually.

Usually, you can get use AvatarAssembler and have Unity do all the work for you. Most of the time it'll work, otherwise, it might be stubborn and you'll just have to merge armature in Blender and then port it to Unity.