Originally named Kyoukya Eaeriaea, Kyoka Midarezaki once reigned as Queen Vanessa over Shangri-la, the demon kingdom beneath the earth. Belonging to a race capable of possessing others' bodies, she felt incomplete despite her subjects' worship. She abandoned her throne and deliberately erased her own demonic memories to live as a human. Her appearance resembles a young girl with violet hair, green eyes, cat ears, and a tail. She matches her husband Ouka's height, remaining the shortest family member except when Gekka takes a jellyfish form.

Through the government initiative "Operation Cozy Family," designed to unite potential destroyers of humanity, she became matriarch of the Midarezaki family. As Ouka's wife and mother to the children, she strives to fulfill domestic roles but draws misguided inspiration from manga and soap operas, frequently causing marital misunderstandings. She exhibits intense jealousy when Ouka interacts with other women. Despite egotistical declarations of godhood and attention-seeking behavior, she demonstrates genuine care and fierce protectiveness towards her family.

Her personality blends arrogance, destructiveness, and hyperactivity, rooted in her past as a worshipped deity. She habitually assigns absurd names to people, insisting they should feel honored. Her cooking is notoriously hazardous, often imbuing food with sentience or ominous auras, terrifying everyone except Hyouka, who lacks taste buds. She communicates telepathically and manipulates minds using an ability named "Keitai Denwa" (Cell Phone), also employing it to control miniature helper dolls. This power enables telepathic conversations with her daughter Yūka.

Her commitment to the family deepens throughout the series. Initially claiming Ouka cannot love, she eventually reciprocates his feelings. Her protective nature culminates in confronting threats to the household, once rallying all members to collectively claim the title of "Great Destroyer" for mutual protection. In the conclusion, she temporarily departs for Shangri-la to reclaim her lost memories, leaving miniature replicas of herself with the family for companionship.