Pure carbon steel with minimal impurities. Proper forging and heat treatment produce blades that are sharp and easy to sharpen. Tungsten and chromium are added to improve heat treatment characteristics and wear resistance, resulting in long-lasting sharpness. A steel grade with rust resistance and easy maintenance by adding nickel and chromium.

Kurouchi Finish, the unprocessed (black) part on the top side of the blade has already developed a dark patina, which protects the blade and gives it a traditional Japanese look.