The Japanese forged knife Kuro-Uchi Nakiri is handmade. The knife blade is three-layered and, what is important for a Japanese chef, double-sided sharpening. The central, extremely thin and durable layer, hardened to a hardness of 61-62 HRC, is made of Blue Paper Steel (or in Japanese, Aogami), which has proven to be the best Japanese blade carbon steel. It naturally rusts - the Japanese traditionally do not use chromium-containing steel, since carbon steel gives a much more aggressive cut and is more resistant to dulling. The outer layers (which serve to prevent damage to the thin, hard, but relatively fragile central core) are made of softer steel, also rust-resistant, partially covered with blackening, which makes it easier to maintain the knife. Prolonged use of the knife will result in a slight darkening of the area that is not protected by the anti-corrosion coating. This will not damage the knife and will not impair its performance, but it will add a nice visual contrast to the outer layers of low-carbon steel, revealing the joint line - an uneven pattern that will resemble the yanangibi line, as on Japanese katanas.