Japan and the West view cutlery completely different.
We will explain these differences by broadly dividing them into two easy to understand categories.
Composition of the Raw Materials
Western knives are made from a single kind of steel material, while Japanese knives are made from a combination of soft iron* and hard carbon steel.
The entire shape of the blade is made out of soft iron while the edge of the blade is made of hard iron. Thus, giving it an ideal sharpness and elasticity often utilizing scarce steels like Tama-Hagane effectively.
Use and Feel of the Blade
It’s said that Japanese people generally pull the blade as they cut, whereas Europeans and Americans press down as they cut. I hear Americans and Europeans say, “Japanese blades cut too well,” but the reason that the user can prepare food while exerting so little force is probably due to the sharpness of Japanese blades.
Since harder blades are better for the kind of pressing and cutting that is common in the West, importance is placed on the HRC hardness scale which denotes the hardness of the raw materials. However, since Japanese knives are meant for functionality with their well-balanced combination of soft iron and hard carbon steel, hardness alone isn’t thought of as the end all.
*Recently, rust-resistant stainless steel is also common