Watch Sword of Desperation

Expert swordsman Kanemi Sanzaemon is, first and foremost, a man of principle. In order to save his clan from the corrupting influence of his lord's favorite concubine, he publicly assassinates her, fully expecting it will result in his own death by seppuku. Instead, he is sentenced to solitary confinement for an entire year, then released under one inexplicable condition: he must now serve as the lord's bodyguard.