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. 幼い頃、あやかしに攫われ体に妖印を刻まれたことで、一族の人間たちから「傷モノ」と虐げられてきた菜々緒。予定されていた白蓮寺家の若様との婚姻も従姉の暁美に奪われ、妖印を隠すため猿面をつけさせられて、惨めな生活を送っていた彼女はある日、紅椿家の若き当主・夜行と出会う。 とある事件により面が外れ夜行に素顔を見られてしまう菜々緒だが、夜行はその美しさと霊力の高さに興味を持ち――。