小刀・小柄・笄

A Kogatana (小刀), or "small sword" in English is a small knife designed to be fitted with a Kozuka (handle). The Kogatana is a small utility knife that fits into a pocket on the Saya.

A Kozuka (小柄), or "small handle" in English is a small Tsuka designed to be fitted with the Kogatana. It usually features various designs inspired by famous historical events or popular Katana-related designs.

The Kogai (笄) is a spike for hair arranging also used for various utility tasks, that fits into a pocket on the saya (similarly to the Kogatana).

The Kogatana and Kogai are the reasons why there are small holes on either or both sides of the Tsuba, so they can be pulled while the Katana is in its Saya.