The model in question is converted from MMD using an addon called MMD Tools. The textures load fine with the base engine, but on Cycles it renders with these odd missing chunks. It seems to happen even if I change the lighting type.
I can't provide the .blend file, but know that sometimes the materials work fine, but it occasionally does this. As you can see, the main outfit, facials, and hair textures seem to be fine. But the arms are weird.