In the turbulent aftermath of Japan's civil wars in the 17th century, a fearsome warrior known as 'the unconquerable' rises from the ashes of the Battle of Sekigahara. Unbeknownst to all, Kyoshiro, a gentle medicine seller, conceals the soul of a deadly assassin within him. Teaming up with a youthful bounty hunter, they traverse the chaotic landscapes of Japan pursuing a killer, all the while unraveling the enigmatic mystery shrouding Kyoshiro's true self.