The Dokoutsui (土荒槌, lit. Earth Barren Hammer) is an iron hammer with the power of earth. Despite being the slowest of Jubei's weapons, it's also the most damaging. Jubei can obtain this weapon from the Dragon Shrine inside the Oni Island, in the first chamber.
Jubei leaps and pounds the soil with the hammer, knocking all the enemies in the area down with bursts of dirt.