In the last days of the Tokugawa shogunate, the era in which the samurai rule is about to end. Those who were called ninja, had become obsolete. Ryu (Kanichiro) is a descendant of the 'Genin', which is the lowest level in a ninja clan, but is now become a fugitive ninja living in Edo. One day, Kaishu Katsu (Kanji Tsuda) discovers Ryu's origin, scouts him and assigns him a secret mission.