It is set in the period between the Battle of Sekigahara in 1600 and the Siege of Osaka in 1614. Years of warfare end in a Japan unified under the Tokugawa shogunate, but the peace is threatened. It follows Sarutobi Sasuke (Kōji Takahashi), a spy for the Sanada Masayuki. Sasuke, tired of conflict, longs for peace. When a high-ranking spy named Tatewaki Koriyama defects from the shogun to a rival clan, Sasuke is caught between two rival groups of spies, those working for the Tokugawa Shogunate and those supporting the Toyotomi Hideyoshi. Tokugawa Ieyasu's clan was in the strategically superior position after having won the Battle of Sekigahara but had engendered much hatred among samurai who had become rōnin after the Battle.