From the introduction: The year is 1613 and the Tokugawa Shogunate is near being torn apart by internal strife. By the will of the ruler of this land two clans who until recently had a non-aggression pact with each other after a 400 year feud will once again meet on the battlefield. The Iga Tsubagakure led by Ogen and the Kouga Manjidani led by Danjou. These twenty ninja, these twenty monsters fight for two sides in a war of succession. You have around a year before this happens and nine more to do whatever you want afterwards.