Ayashi no Ceres is about a girl named Aya Mikage who leads the life of a normal high school student until she turns 16. On her 16th birthday, her own family tries to kill her and imprisons her twin brother Aki. Aya later finds out that she possesses the blood of the "tennyo" (heavenly maiden), and when severely shaken she will transform into Ceres. If left to live, she is destined to bring ruin upon the Mikage family.