When Nanao was a child, she was kidnapped by an ayakashi who carved a demonic seal on her body. Her planned marriage to the Waka-sama of the Hakurenji family was stolen from her by her cousin Akemi, and she was forced to wear a monkey mask to hide her demon mark, leading a miserable life. Then, she meets Yako, the young head of the Benitsubaki family. Nanao loses her mask due to a certain incident, and Yako sees her true face, but Yako takes an interest in her beauty and spiritual power.
