Ryoma Amami is a samurai living in the imperial palace who discovers a demon invasion of Edo Japan has been launched. He realizes that his boss and man he swore his life to, the emperor, has been possessed by the demon snake king, Orochi. Barely escaping the palace with his life, the hero turned ronin - a lowly, wandering samurai without a master - must form a team of misfits willing and able to trek around the country, discover and harness the power of mystic talismans, and combat the new, demonic foe and its army.