A kodachi (小太刀) is a short tachi, typically with a blade length of under 60 cm, making it distinct from both a standard tachi and a wakizashi. Unlike the wakizashi, which was paired with a katana in the later samurai period, the kodachi was primarily an independent weapon, often used during the Kamakura (1185–1333) and Muromachi (1336–1573) periods. It was favored by warriors who required a shorter but still powerful cutting weapon, such as foot soldiers or those in confined combat situations.

Sugata (姿, Blade Shape)

• The kodachi retains the deep koshi-zori (腰反り, curvature near the tang) seen in a tachi, making it different from a wakizashi, which often had a straighter profile.
• The blade typically measures 45–60 cm, placing it between a wakizashi and a full-sized tachi.
• The overall proportions follow tachi-style sugata, making it effectively a scaled-down tachi rather than a short katana.

Mountings (Koshirae, 拵え)

• Kodachi were often mounted in tachi-koshirae (太刀拵え, suspended scabbard fittings), reflecting their battlefield use.