The Shogun's Vault IV: The Gold Mines of Sado.

Account magistrate Wakisaka Bizen Mamoru asks Yoshibei, the chief priest of Iriya and Myohoji Temple to explore the Sado Gold Mine. They suspect that large amounts of money are being diverted to somewhere else. Yoshibei, a former official secret-head accepts the job and recruits three skilled Karadogumi… Nanikiri, Hayashi, and Kumonryo. In Sado, where the four infiltrate, the magistrate Okubo Hitachi Mamoru who plans to overthrow the shogunate is trying to buy a large number of firearms from Russia.