Katsuro, a young samurai on the last stop of a tour of the domain on behalf of his lord, is in the town closest to the castle when a battle breaks out. The only survivors seem to be Katsuro, a Buddhist monk, and a Shinto priestess. When Katsuro hurries to inform the daimyo in the castle, he finds the man has been murdered in his bed. Overcome with grief, Katsuro is on the verge of committing ritual seppuku when he remembers that he has a reason to live: the daimyo's son. Accompanied by the monk and priestess and a masterless samurai they encounter along the way, Katsuro sets out to perform his final duty as Lord Morishiro's first samurai. He will protect the young man and do everything in his power to see that he is able to take his place as ruler of the land.