At the end of the Edo Period which brought the era of the samurai to a close, Ryu is the descendant of a "genin", the lowest rank in the ninja hierarchy. Due to such a low rank, he lives a miserable existence. Then a secret order is received from Katsu Kaishu bidding for the recovery of princess Shizuka, a Satsuma native, from the home of a prominent vassal in Edo.