How to Get Odachi | Ghost of Yotei

Odachi is the opposite of Dual Katana, where the Odachi is slow and offers powerful attacks. You only need to hit the enemy once, and they're done. The Odachi is the epitome of power; it can break the enemy's defense. Odachis are effective against large and heavily armored enemies.

Progress through The Saito Brothers Main Quest and talk to Master Yoshida.