From ANN:
Yasuori Kato, an oni who mastered the art of onmyodo and shugendo, is determined to destroy the Imperial Capital Tokyo to appease the grudges of his ancestors. To accomplish this, he attempts to awaken a powerful angry spirit, Taira no Masakado, to use as a tool for his destruction. When his initial attempts fail, Kato seeks out Masakado's descendant, a young woman with psychic powers, to use as a medium to communicate with the spirit. Opposing Kato's efforts is Yasumasa Hirai, the greatest onmyoji in all of Japan as well as the Soma Family, another lineage of Masakado. The conflict that results from this encounter will shape the history of Tokyo.

Based on books 1 to 4 of the novel series Teito Monogatari (1985-1989).