It is the Warring States period, a time of storms. A young man hunting deep in the mountains meets a young woman bathing in an open-air bath. The woman's name is Oboro, the daughter of a ninja leader. The man is Ayamaru, the fifth son of a fallen samurai family. Ayamaru falls in love with Oboro at first sight and accompanies him to the ninja village. With a manpower shortage, the leader gives Oboro and Ayamaru a secret mission. However, on the way, they encounter a major earthquake!