Inu-oh

A withered biwa player narrates a tale of how 900 years ago, the Genji clan sought the Imperial Regalia to unite the emperor's throne. They defeat the rival Heike clan at the Battle of Dan-no-ura, wherein the child emperor drowns while carrying the Grasscutter Sword. Three hundred years later, agents of Ashikaga Yoshimitsu hire young Tomona and his father to retrieve a box from a Heike shipwreck. They find a sword inside the box. Not realizing that it is the Grasscutter Sword, Tomona's father unsheathes the sword, letting loose a blade of energy that cuts him in half and blinds Tomona. Tomona then goes on a years long journey to find answers for what happened, with the ghost of his father accompanying him. He meets a member of a whole troupe of blind biwa players, and decides to learn the biwa and join the troupe. Tomona changes his name to "Tomoichi", but the name change makes it difficult for his father's spirit to find him.