In 1614, the shogunate annuls a centuries-old truce between the Kouga of Manjidani and the Iga of Tsubagakure, ordering each clan to send ten of its deadliest shinobi into a battle to the death. The victor decides which Tokugawa heir takes the shogunate. Caught at the center are Gennosuke of Kouga and Oboro of Iga, the clans' young leaders, betrothed in the hope their marriage would end the feud. The order forces each to choose between killing the one they love and watching their clan destroyed.