Five years ago, Musashi made a promise with his friend Kojirou Kanemaki that once they grew up, they would become samurai, form a league, and go on demon-slaying quests. But since then, things have changed. With demons now being praised and worshipped by society, the samurai are shunned and disgraced. Afraid of revealing his dream of becoming a samurai, Musashi blends into the town's dogma by becoming a miner while secretly polishing his swordsmanship.