Two seriously wounded samurai find refuge from a storm at an isolated temple, the home of a swordsman and a mysterious young woman. One samurai awakes to find that not only has his comrade died, but that his wounds have miraculously healed. He discovers that he has been given the power of immortality by the swordsman, a man once known as the legendary Miyamoto Musashi, who now lives an endless existence as Aragami, a "god of battle".

In war-torn Japan, the Tokugawa Shogun, desperate to restore peace to his people, orders the assassination of the hostile warlords. A beautiful young woman is raised from birth with nine other orphans, to become an assassin. Her name is Azumi, the ultimate assassin.