It is the first film of Hiroshi Inagaki's Samurai Trilogy of historical adventures. The film is adapted from Eiji Yoshikawa's novel Musashi. The novel is loosely based on the life of the famous Japanese swordsman Miyamoto Musashi.
Following the battle of Sekigahara, Takezo (Toshirō Mifune) and his friend Matahachi (Rentarō Mikuni) find themselves on the losing side. Instead of the grand victory and glory Takezo had anticipated, he finds himself a hunted fugitive. (wikipedia)