Mika is the ruler of the Higashigetsu Fūma Witch Academy, who is setting forth the domination of all the female students through her right hand, Kaon. She displays signs of jealousy fueled by possessiveness when observing Himiko provide Kaon with energy and apparently has a vindictive streak as she punishes those of her subordinates who fail her. Furthermore, she displays signs of megalomania and extreme egomania. Mika is the third eldest child of the Ayanokōji family. She seems to have heterochromia, with her right iris being purple and the other orange; it is later implied that the orange eye may in fact be an implant. Mika suffered injuries during the 'Days of Hot Snow' which obliged her to have hospital stay and she is shown with a bandage covering her left eye. Years later, she seems to be suffering from a potentially debilitating medical condition, despite her usual poise and her much-lauded graces, which is possibly exacerbated by her tendency to provide Kaon with too much of her own Mana.

Mika's own words betray that she desires Murakamo to love no one but herself and she expresses a malicious jealousy and contempt of Himiko, who is much deeper in Kaon's affections than she can apparently hope to be. Mika's flashbacks to her time in the hospital imply that she has fixated on Kaon because she reminds her of a nurse who took care of her at that time. Other people who bear the brunt of her bile are her elder brother Kazuya, whom she hates absolutely for everything he ever did including the manner of his death, and her younger brother Kyōshirō, who she considers to be 'the demon's tail', with Kazuya being 'the demon'. Mika's intense hatred for Kazuya seems to have originated during her early teens, when he stole away a girl she was developing an affection for, apparently with the explicit intention of hurting his sister's feelings.

Before her death, she entrusted Himiko to rescue Kaon from Kazuya and to that end gave her the key to a device she created based on plans drawn up by her grandfather Reito. This device is a type of bass guitar capable of creating a harmony to suppress Mana, thus causing pain to an Absolute Angel - or Kazuya.