Kasumi knives are produced by the Sumikama Cutlery in Seki Japan. These knives are made from 33 layers of stainless steel. Only the middle layer acts as the cutting edge, and it is made using V-Gold No. 10 stainless steel. V-Gold No. 10 is a high carbon stainless steel with cobalt, manganese, molybdenum and vanadium for added durability and ease of sharpening. V-Gold No. 10 is a high quality steel developed exclusively for knives and scissors. The addition of cobalt to this steel requires special tempering in order to maximize the full benefit of this steel. Sumikama's technique for this special tempering is a closely guarded secret.
The layers on both sides of the V-Gold No. 10 core are made by repeatedly folding together two different types of stainless steel and forge welding them by hand until you have sixteen exceedingly thin alternating layers. These sixteen layers are then forge welded to both sides of the V-Gold No. 10 core.
The edge on a Kasumi knife is beveled like a western style knife. However, the bevel is much larger than the bevel on a European or American brand. This larger bevel creates a sharper edge. Kasumi knives do not have a bolster. They do have a stainless steel ferrule that is forge welded to the blade to ensure that food particles do not become trapped between the blade and the handle. They also have a full tang. The handle is made from multiple layers of wood impregnated with a plastic resin. The handle is riveted to the tang.