What is Yakizume Boushi in Japanese Katana terminology?

The term ""焼詰帽子"" (Yakizume Boushi) refers to a type of tempering pattern on a Japanese sword where the hardened edge (nie) does not return, but instead continues to flow towards the back of the blade. This pattern is often seen in the works of the Houshou school, Senjuin school, Tegai school, and Taima school, which are part of the Yamato tradition. The pattern often appears as if it has been swept across the blade.

In cases where the tip of a naginata or a nagamaki has been reshaped into a sword, the return part of the tempering is removed, resulting in a Yakizume Boushi. This pattern is a unique and artistic expression of the swordsmith's skill, and it is highly valued by sword enthusiasts and collectors.