Tsukiji Masamoto White Steel 1 Fuguhiki 300mm (11.8")

Kasumi knives like this Fuguhiki (Fugubiki) are produced by hand-forging high-carbon steel (white steel 1) with iron. The carbon steel becomes the knife's cutting edge while the iron forms the spine and body of the blade. This combination of Steel Types creates a knife that is less brittle than the honyaki-style, and easier to sharpen. Many carbon steel knives are made using coke fuel but Tsukiji Masamoto knives are made using charcoal, which produces higher quality blades because of the gradual rather than abrupt temperature change.
Tsukiji Masamoto pays special attention in creating a deeper urasuki (concave surface of the backside) to maximize its effect. Urasuki facilitates clean food separation from the blade, just like hollowed or perforated knives. This is why you can perform uraoshi (sharpening the backside of a single bevel knife to keep the outer edges leveled) on a coarse stone, unlike most other brands.
Carbon steel blades like this kasumi require more delicate handling and care than stain-resistant knives, but are sharper. Kasumi knives are the standard blade of Japanese chefs.