Sugimoto Kasumi Superlative Sugimoto cutlery has been making knives since the 1930s. After WWII they were the first company t begin producing western and Chinese style knives for the Japanese market. They make fine quality knives and hand finish each blade. These are extremely sharp knives and we are proud to add them to our line up of top quality knives. Sugimoto Kasumi Superlative knives are made from White Steel. The RC hardness of the Japanese Kasumi Superlatives are RC 63 ~66.