Considering the knife making process two different techniques can be distinguished.
Kitchen knives entirely made with high carbon steel using the “honyaki” forging technique (similar to the one used to forge swords).

This technique consists of heating and hammering together chunks of molten steel until they take shape. After heating and hammering, annealing, quenching and cooling steps confer to the steel its hardness and ability to keep an edge.

Kitchen knives made with a combination of soft iron and high-carbon steel using the “awase/kasumi” forging technique. This technique consists of layering soft iron on top of red hot carbon steel. It takes the shape of a kitchen knife as heat is applied. High carbon steel forms the cutting edge while the soft iron a strong spine and tang.