A Nara School Kozuka. Japan, Edo Period, 19th century. Crest: Prince Koriyama of Yamato Decorated with incised swastikas in squares, squares with nanako ground and a diamond quatrefoil, the crest of the Koriyama clan of Yamato province.

A Kozuka is the small knife stored in Kozuka Hitsu (groove of the sheath of the Japanese sword). Many Tsubas (handguards) have two holes to put Kozuka and Kougai (equipment for appearance) next to Nakagoana (a hole of the Tsuba to put sword), so that Samurai didn’t need to draw his sword out of the scabbard when he wanted to use Kozuka or Kougai. Initially, Samurai used it for cutting wood or attacking enemies in an emergency. It is said that Kozuka was used as a craft knife rather than a weapon.