刃区焼込み (Hamachi Yakikomi)

What is Hamachi Yakikomi in Japanese Katana terminology?

Hamachi Yakikomi refers to a type of blade pattern (Hamon) in Japanese swords. Unlike the usual pattern where the blade pattern (Hamon) (Hammon) starts from the "刃区" (Hamachi: the notch on the edge of the blade), in Hamachi Yakikomi, the tempering starts deeply from below the Hamachi. This results in a unique pattern where the tempered area extends into the base of the blade. This technique requires a high level of skill from the swordsmith, as it involves controlling the heat treatment process to achieve the desired effect.