The Lone Wolf, a skilled swordsman known for his mastery of butt-sword fighting techniques, embarks on a journey with his family in search of employment. Along the way, they meet a mysterious girl named Hazumi and a wild dog named Shiro, and decide to join forces for the journey. However, their travels are met with danger, as they are attacked by various assassins, ultimately leading to a perilous showdown against the armpit-swordsmen of the Demon Bull Clan - the sworn enemies of the butt-swordsmen. As the battle between butts and armpits ensues, Hiroshinosuke Nohara and his son Shinnosuke have the opportunity to showcase their swashbuckling skills while facing off against an eclectic cast of adversaries.