What is Ichi-mai boshi in Japanese Katana terminology?

The term "一枚帽子" (Ichi-mai boshi) refers to a type of Japanese sword in which the entire tip (kissaki) is tempered. This type of sword is often seen in the Koto period, a time when swords were frequently used in actual battles. By deeply tempering the most vulnerable part of the sword, the tip, it made it possible to resharpen the sword. This was a practical design choice considering the frequent use of these swords in combat situations.