Been re-reading Eiji Yoshikawa's Musashi because my wife had listened to the audiobook. She loved the story but couldn't keep track of all the characters, so I've been compiling a chapter-by-chapter character guide for her with links when a historical figure shows up in the story.
Not just an interesting concept. It's an epic based on real events. Miyamoto Musashi actually won a duel by carving a wooden sword out of a broken oar.