This is a classic early Japanese Ninja movie. The Iga ninjas are a dying breed as Toyotomis rule allows Japan to experience some peace. Juzo, an Iga ninja who had vowed revenge for the death of his family, is hired by a rich weapons merchant to assassinate Toyotomi, restarting his quest for blood. In his way are rival ninja, and his once best friend who has decided to become a government vassal. The main plot centers around the conflicts that confront Juzo. The largest of these is the conflict between Juzo and his oldest friend, Gohei. Then there is the conflict each of these characters has with their respective women, whom are also Ninja in their own right. Finally Juzo is faced with the ultimate conflict between duty and happiness. Can he complete his mission of assassinating Toyotomi? Or will he choose a life of happiness and fulfillment with his woman? There was a remake of this classic in 1999 entitled Owl's Castle, but for people that have seen both versions, this first version, Castle of Owls, stands as the penultimate adaptation of the classic Ryotaro Shiba novel "Ninja hicho fukuro no shiro".