One thousand years ago in the ancient Japanese capital of Heian-Kyo mortal men live side-by-side with demons. A the Mikado's court, wise soothsayers control the demons with spells and incantations - these are the Yin-Yang Masters. The most enigmatic of these is Abe no Seimei, a sly fox of a sorcerer, who astounds with his magic and flouts court rules. Under his wing comes his new apprentice, the eager but naive Hiromasa. The pair wander the ancient city, Seimei working his magic to solve supernatural crimes. With the help of an immortal woman Lady Aone they must save the city from the forces of evil - the wrathful spirit of Prince Sawara - and find out who is behind the plot to destroy the hereditary imperial line.