As most people know, this is Shakespeare's Macbeth rendered by Kurosawa into Noh format for cinema. Not for nothing is Akira Kurosawa regarded as Japan's greatest director, for this is the best cinematic version of any Shakespeare play (and also one of Kurosawa's best films). Kurosawa had the advantage of working in a different language (Japanese), so he didn't have to agonize over the usual dilemma - whether to use Shakespeare's rotund oratory and blank verse (which is glorious, but goes badly on screen). Kurosawa essentially translates Shakespeare's poetry into visual images, while keeping dialogue to a minimum. He also had the good fortune of accessing two great cultures - European literature and Japanese visual art (he was originally a painter before entering cinema as a set-designer). There are many painterly images reminiscent of Ukiyo-e (e.g. Washizu full of arrows).
The Noh style of acting (like Kabuki, but more refined) seems stilted and exaggerated for the first few minutes; then you realize that is ideally suited to a story like this - more natural acting would seem out of place, as other Macbeth-movies go to prove.
The Japanese title of this film translates as "Cobweb Castle" (or Spider City) and this really should have been the title in English. The film is full of the notion of spiders spinning webs (and plots) in secret. It is worth noting that the witch (or "monster") is first seen with a ghostly spinning-wheel. This symbolizes the thread of fate, but also reflects the cobweb theme.
The story is sometimes slow-moving, but you have to realize that this is a story of insidious slow rot (hence the references to spiders and cobwebs). The decay is punctured by occasional bursts of violent action, as befits the story. The black-and-white picture adds to the creepiness, and the atmosphere is so thick that the movie works more effectively than "Ran" (Kurosawa's more polished Shakespeare-adaptation).
Macbeth is the great-granddaddy of the entire horror genre, and Kurosawa is a worthy descendant.
