Onmyodo is a traditional Japanese form of occultism based on Chinese philosophy and influenced by Japanese culture and religion. Its professional practitioners were called the Onmyoji, and this film is about one of the most famous, Abe no Seimei. Abe is asked by a bumbling court noble to defend the emperor from an evil Onmyoji who is unleashing a horde of Yokai (spirit monsters) to bring about the government's downfall. Originally a novel, it became a comic and then a highly stylized film. A hit in Japan, it has strong cultural overtones, meaning most Western audiences will miss a lot of subtext if they aren't familiar with the Heian period of Japanese history.