The Japanese word Gyuto (牛刀) literally translates to beef sword. The gyuto is the equivalent of the Western chef's knife, and is designed to cut everything: vegetables, meats and fishes. It is made to be used with the push-cut method, lifting the blade between each cutting motion, or with the rocking motion method. It is important that the blade is straight upon impact with the cutting board to avoid damage to the knife edge.
The city of Sanjo in Niigata Prefecture has been famous for its blacksmithing since the 1600s. In the early years, they mainly forged nails by hand. Then, from 1660, different forging techniques were introduced by blacksmiths from Aizu. Thanks to this, the blacksmiths of the city began to diversify their production. The quality of Sanjo's tools and knives enjoyed a strong reputation in Japan at that time, and it still does today.
Simply explained, Aogami #2 developed by Hitachi Metals is a steel made from Shirogami #2 in which some chromium and tungsten are added for better durability and corrosion resistance. In addition to that, the higher carbon content of the steel allows for better cutting retention. Objectively, the Aogami #2 is an improvement over the Shirogami #2. For patina lovers, however, Shirogami steel will be more reactive to oxidation and could be an advantage.