Having been demoted for failing to prevent the murder of one of his superiors, Mondo is startled by a group of masked thugs who are soon attacked in turn by an unseen force. He begins to suspect the work of assassins, but whose side are they on?

In the final days of the Edo shogunate, a government commander enters Edo Castle to inspect the Ōoku. Ignoring warnings, he steps into a forbidden room where, 200 years before, Lady Oyuki, a favored concubine, was forced to commit suicide by Tokugawa Tsunayoshi over a suspected affair. Consumed by vengeance, her spirit continues to haunt all those involved in the tragedy.