Rabbit Mika began existence as Mikazuki, a pet rabbit gifted to Gorō Mutsumi by a neighbor. Her name commemorated the crescent moon visible when Gorō received her. Tragically, she perished from isolation after Gorō traveled to care for his sick grandmother, leaving her alone for an extended period; she succumbed to loneliness before his return.

Reincarnated as a guardian angel, Mika now holds Senior rank among the twelve. Rabbit-inspired elements define her appearance, most notably her hairstyle resembling rabbit ears. Orange serves as her designated color, and her physical measurements show slight variations between seasons. Her death manifests as autophobia, an intense fear of being alone. This phobia fuels pronounced attention-seeking behavior and a desperate need for companionship, particularly from Gorō.

Her personality exhibits extroversion, hyperactivity, and overt romantic attraction toward Gorō, setting her apart from most angels. Impulsive actions frequently lead to conflicts, especially with Ayumi (turtle) and Akane (fox), echoing historical animal rivalries. She actively dresses Gorō according to her fashion tastes and indulges in fantasies about a romantic future with him. Despite self-centered tendencies, she displays protective instincts during serious situations and offers assistance to fellow angels, such as helping Nana.

Across seasons, her core motivations consistently focus on winning Gorō's affection and overcoming her deep-seated fear of neglect.