Hatsume is a kunoichi -- a female ninja -- sent by Ieyasu Tokugawa to assassinate Mitsunari Ishida, whose small fiefdom is all that stands in the way of total domination of Japan by Tokugawa. However, after taking resourceful steps to get close to Ishida by becoming his concubine, Hatsume inadvertently finds herself in love with the straight-minded Ishida, and goes from assassin to protector as Tokugawa sends a new ninja squad to Ishida's castle to finish the job. Will Hatsume and Ishida live to fight the crucial battle for Japan's future that lies ahead?