During Japan's Sengoku era, a young orphan named Kotarou and his loyal dog Tobimaru resort to stealing to survive. Their lives take a drastic turn when Kotarou becomes the target of Ming Dynasty assassins for unknown reasons unrelated to his petty thefts. Encountering Nanashi, a wandering samurai seeking refuge, proves to be their salvation after a deadly attack leaves Tobimaru poisoned. Despite Nanashi's initial reluctance to assist further, a reluctant agreement is struck when Kotarou offers a precious gem in exchange for protection until Tobimaru recovers and they reach their destination. Embarking on a treacherous journey, the trio faces increasing peril as a formidable Ming Dynasty swordsman is dispatched to capture Kotarou and fulfill a mysterious prophecy.