Sword of Kamyi

Jiro finds his mother and sister murdered in his home and is falsely accused of the crime. He flees his village and meets Tenkai, a priest who tasks him with killing a rogue ninja named Tarouza. This act sets Jiro on a path to become a master assassin through training. Years later, he discovers he was an orphan, his real father was Tarouza, and the events that led to his parents' death were connected to a larger scheme by Tenkai.