Honyaki
Honyaki knives are forged from one single material, usually high-carbon steel. The finest honyaki (mizu-honyaki) are then differentially-hardened, the same method used for traditional katana. Their sharpness is the longest lasting of all Japanese blades. They are extremely difficult to forge, requiring a high level of skill and experience. They are also very difficult to sharpen and maintain, and easily damaged if not properly used. They are also more expensive than other knives (costing over $1000 for a 240mm gyuto),[1] such as Kasumi knives, which are made out of two materials and are easier to forge and maintain.