“Careful, Your Grace. Nothing cuts like Valyrian steel.”
-- Grand Maester Pycelle to King Joffrey, Game of Thrones.
The katana is the traditional sword of the samurai.
This simple sentence conceals two millennia of dense historical narrative, from intricate naming conventions to astoundingly complex usage traditions. Not much in Japanese culture is simple.
The Japanese do not compromise on quality
The same time tested forging tradition that led to the exceptionally strong katana, is used in the production of Japanese steel for household implements ranging from pruning shears to kitchen knives. The Japanese were not prepared to leave excellence on the battlefield.
The secret to Japanese steel is the variation in carbon content used in different layers of the blade. This came about because the iron of medieval Japan was of a fairly low quality. Smiths found that by folding the metal evenly and repeatedly in the forging process, they could work out much of the impurities. This incidentally resulted in a core of very hard, very pure steel and an outer layer with enough carbon to allow for a strong but incredibly sharp cutting edge.
Curvature is achieved not by brute force, but a pattern of differential heating and cooling resulting in the most evenly distributed tensile strength and purity that is possibly outside of the geological process resulting in diamonds.
The result is a range of specialized blades in keeping with the Japanese philosophy of using the correct tool for the job. This philosophy permeates Japanese culture and takes a central position in Japanese cooking. The gracefulness of the knife is believed to carry over into the food; the heart and soul of the chef becomes an extension of the Japanese mind.