Ai Kamiyo is a high school student who becomes the second tutoring pupil of the protagonist, Keitaro Gentoga. Her life has been profoundly shaped by a tragic supernatural heritage. The Kamiyo family carries a curse where its women are chosen to become a yorishiro, a physical vessel or medium to which a god is bound. As a result of an ancestor's mistake, the family is fated to be a plaything for a malevolent deity from generation to generation. Because of this, Ai was forced to leave her family home as her very presence brought misfortune to them. Her older brother took her in to live with him, but he was later killed in a freak accident involving falling construction materials when he pushed Ai out of the way. This event left her feeling deeply isolated and psychologically vulnerable.

Ai presents a contrasting exterior to her tragic circumstances. She has a gyaru fashion style, characterized by a colorful school uniform and long blonde hair. Her most distinct feature is the star-shaped symbols that appear in her eyes, which are not a fashion choice but a physical stigma, a mark indicating that she is dedicated to and claimed by a god. Despite the misfortune that surrounds her, she maintains an openly joyful, over-friendly, and exuberant personality. She is energetic, has excellent social skills, and often craves sugar to help her focus on her schoolwork. However, this cheerfulness is a conscious effort to cope with her situation. Underneath the surface, she struggles with a fatalistic outlook, believing that her life is destined to bring ruin to those around her.

Ai's primary motivation is to escape the supernatural forces that have ruined her life. When she meets Keitaro, she quickly senses his knowledge of the occult and, despite having just met him, desperately asks for his help. She is initially troubled by what she believes is the malevolent ghost of her brother. As the story unfolds, it is revealed that the god who has claimed Ai is the true source of her suffering. The god views Ai as its possession and acts as a deterrent, chasing away other evil spirits that are drawn to the divine energy she emits. However, the god does not protect her from harm; rather, the misfortunes and accidents that occur due to attracted spirits are diverted onto the people nearby, leading to her brother's death. Ai's goal becomes not just to be free from ghosts, but to break the divine curse on her bloodline and reclaim her own future from the god that considers her its future bride.

Within the story, Ai serves as a major supporting character and a new ally for Keitaro and the young spirit medium Yayoi Hozuki. Her introduction marks a significant escalation in their mission, moving from capturing ordinary evil spirits to confronting a genuine deity. Ai’s role is that of a catalyst, providing a personal and urgent reason to take on a god-level threat. She also brings a different dynamic to the group, with her lively and talkative nature contrasting with the more intense personalities of her companions. Her relationship with Keitaro is that of a student to a tutor, but it quickly deepens as he sees his own past vulnerability in her and is determined, as her teacher, not to abandon a student in trouble. With Yayoi, she forms a quick rapport, looking up to her as a powerful and reliable senpai despite Yayoi being younger.

Ai undergoes significant character development as she confronts her destiny. Initially resigned to her fate, she is overwhelmed by the belief that her curse will never end and that she is better off disappearing. Witnessing the resolve of Keitaro and Yayoi, who actively fight against the supernatural to save her, gives her the strength to fight her fatalism. She makes a vow not to be downcast anymore, choosing to live and face her future with her new friends. Later, while recovering from an unrelated incident, she experiences a terrifying nightmare in which she is forced into a wedding dress and begins to lose her identity and memories, transforming into a faceless entity like the other women claimed by the god. This vision serves as a horrific reminder of her fate and strengthens her resolve to stay connected to Keitaro and Yayoi, who represent her only hope for salvation.

Ai's most notable ability is not one she can control but is a consequence of her status as a yorishiro. The star-shaped marks in her eyes are proof of her contract with the god. Because the god dwells within her, she emits a powerful spiritual energy that constantly attracts other malevolent ghosts. This makes her a supernatural beacon. Simultaneously, the possessive god acts as a deterrent, instinctively warding off or attacking other spirits, which paradoxically offers her a dangerous form of protection. She herself does not possess any active spiritual powers or exorcism techniques, making her role in the group that of a crucial mission objective and a living link to the divine enemy they seek to defeat, rather than a combatant.