A little uncertain about the tags for this image. The extra limbs are referred to as 義腕, which does translate to "prosthetic arm." However, the page for prosthetic_arm uses 義手 instead. This might be to distinguish the fact that Fiore's prosthetic arms are extraneous limbs, rather than replacements for missing limbs.

Still, I think the tag "prosthetic arm" probably fits the best, unless there's another one that I'm forgetting.