Ayaka Kagari is a central figure in her narrative, known as the Princess of Tougetsu Academy, a title that signifies her status as the most popular and accomplished student in the school. She is the daughter of Kazane Kagari, the powerful chairwoman of the academy, and belongs to a group known as the Workshop Witches, whose mission is to monitor and regulate other witches who might misuse their powers. Her life takes on a deeper, hidden purpose as the sworn protector of her classmate, Honoka Takamiya.

Physically, Ayaka is striking and unmistakable. She is notably tall, towering over most other characters, with long black hair and green eyes. Her bearing is regal and serene, and she almost never displays any overt emotion, maintaining a stoic and expressionless facade that makes her difficult to read. Beneath this cool exterior, however, lies a singular and overwhelming devotion to Honoka Takamiya. While she appears indifferent to the adoration of her vast fan club and the daily affairs of the school, her entire demeanor changes when Honoka is involved. She becomes fiercely protective, displaying a lethal temper towards anyone who threatens or even annoys him, whether a powerful Tower Witch or a simple school bully. This devotion borders on obsession; her actions include stalking him through over eighty middle schools to find him, taking candid photos, and creating handmade dolls in his likeness.

Ayaka's role in the story is primarily that of Honoka's bodyguard and protector, a duty she performs with absolute seriousness. Their connection is formalized by an ancient contract, which has profound implications for their dynamic. As long as she is near him, Ayaka can draw upon Honoka's immense, hidden magical reserves to amplify her own power. Furthermore, any wounds or damage Honoka would receive are instead transferred to her, making her his shield in a very literal sense. This contract also makes her betrothed to him, as their mothers arranged the marriage, a fact that Ayaka herself seems to eagerly anticipate. Her motivation is singular: to ensure Honoka can live a normal, peaceful life, a goal she pursues by any means necessary, from using her authority to keep them in the same class to personally tutoring him for university entrance exams.

The narrative gradually reveals the enigmatic and tragic depths of her background. Cryptic flashbacks suggest that her childhood was far from ordinary, involving being chained up and subjected to cruel experiments as part of a scheme by the Kagari clan to create the most powerful witch. It is eventually revealed that she is not Kazane's biological daughter, but rather the host for a powerful fire demon or entity named Evermillion, which is now sealed inside Honoka. Honoka, in a past they both cannot fully remember, saved her from this imprisonment and took the demon's seal upon himself, a sacrifice that inverted their roles and forged the bond they now share.

As a Fire Witch, Ayaka's abilities are immense and destructive. She can create and manipulate fire at will, and her body itself is said to be made of flames, granting her a high degree of invulnerability to physical attacks. Her power escalates dramatically when she taps into Honoka's magical energy, allowing for rapid regeneration and even more potent flame attacks. In this enhanced state, she can enter a form known as Overdrive, where her hair turns white and she can summon a dragon familiar. Beyond her magical prowess, Ayaka is also a superlative physical combatant. Due to harsh training from her mother, which included hunting wild beasts with her bare hands, she possesses immense strength and can defeat enemies even when stripped of her magic. Her only true weakness is the contract itself, as her power is diminished and she is vulnerable when separated from Honoka.