Kasumi 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 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 forged-welded to both sides of the V-Gold No. 10 core. 

The edge on a Kasumi knife is beveled. However, the bevel is a much narrower angle than the bevel on a European or American brand. Kasumi knives are beveled at a 15-degree angle creating a very sharp edge. 

The knife has a full tang with pakkawood riveted to each side of the tang creating a very distinctive and comfortable handle.  A pakkawood handle is made from multiple layers of wood impregnated with a plastic resin.