Aya is a typical sixteen-year-old High School student, who is very close to her younger brother, Aki. However, on the night of their sixteenth birthday, her life was turned upside down when she discovered that she is a medium for Ceres' spirit and current host. Because of this, she is forced to separate from Aki and hide away from her family, who are determined to kill her. She strongly befriends people who protect her. However, she wanted to die because Chidori Kuruma, Miori Sahara, and Shuro Tsukasa died for her sake. But, Aki told her that Toya is waiting for her. Toya is her main protector and she falls strongly in love with him, and eventually conceives a child with him.
After the final battle, Aya and Toya start living together as a full romantic couple. She gives birth to a daughter named Miku who slightly resembles Ceres. Three years later, she gives birth to a son whom she names Aki after her younger brother because he is Aki's look-alike reincarnation.