In ancient times, there was a celestial maiden named Ceres who descended from the heavens to bathe in a stream. She hung her robe on a nearby tree as her key to returning home. However, someone stole her robe and forced her into marriage with a man, resulting in a family of mixed human and tennyo bloodline. In modern times, Aya Mikage is a descendant of Ceres and possesses significant tennyo powers. On her 16th birthday, she and her twin brother are thrown a party by their grandpa, who plans to kill her because of her unique abilities. Despite having the power to transform into Ceres and potentially destroy the family, Aya can switch back at will. She is accompanied by protector Yuuhi in this battle against her evil grandfather. However, her relationship with an ex-worker may pose a distraction from her mission.