It is often you get the chance to see this. The chef uses a razor-sharp knife, I mean razor-sharp, and shaves the skin off the top-side of a locally caught Japanese flounder. The flounder has an top-side and a bottom-side, the sides are both used to help camouflage the fish.
Watch the chef’s backhand twist as he manipulate the fish to leverage the knife and the skin. The movements are very controlled and this technique has been developed over 40 years of practice. What is amazing is, seldomly, if ever the chef cuts his fingers.
I admit that I have cut myself several times with my “hocho” and it slices skin off or the finger. Luckily I still have my fingers.