In the year 804, a young Japanese monk Kukai nails a Chinese emperor to the court to perform an exorcism rite. The ruler has fallen into a strange state and has not closed his eyes for a week. But the monk does not have time to help – the emperor emits a spirit right before his eyes. Kukai senses the presence of a cat in the palace, and soon he and his new acquaintance – the imperial clerk Bo Juyi – will have to investigate the chain of terrible events associated with the demonic black cat.