Mirabelle Haywood, originally named Aiko Senoo in Japanese media, relocates with her taxi driver father due to his work. Initially perceived as rude, she quickly befriends the main protagonists once they recognize her unintentional bluntness lacks malice. Her path to becoming a magical apprentice begins after witnessing magic cause her father's duplicate to vanish, revealing the secret magic shop and compelling her to join for its protection.

Hailing from Osaka, she speaks with a distinctive Kansai dialect, localized as a country accent, and dislikes others imitating her speech. Her comedic timing shines, matched by sharp bargaining skills. Naturally athletic, she excels in nearly all sports but struggles with swimming—a skill she failed to learn in childhood, partly blaming her father's teaching methods. Despite her talents, she remains humble and welcomes challenges, though others frequently rely on her for help or advice.

Her personality blends practicality, maturity, and a boisterous sense of humor. She shoulders significant responsibilities, managing household duties for her single father, reflecting self-reliance developed early. During her parents' divorce, she pragmatically chose to live with her father, recognizing his greater need for support. While often appearing cool and level-headed, she conceals deep insecurities and emotional vulnerabilities tied to her past, becoming flustered if seen crying or acting childishly in public.

Substantial emotional baggage marks her background. As a young child, neglected while playing alone, she sustained an injury. Waking in the hospital, she overheard her parents arguing over the incident; she internalized blame to calm them, but their conflicts persisted, leading to divorce. This trauma left lingering guilt, particularly toward her deeply missed mother, whom she meets secretly. She also harbors a fear of violent older men, rooted in witnessing her grandfather abuse her mother.

As a magical apprentice, sky blue represents her. Her transformation phrase is "Pretty Witch Aiko-cchi!" (localized appropriately). She masters broom flight swiftly, becoming the first to ride cross-legged. Her spells include "Pameruku Raruku Rarirori Poppun!" for general magic and "Pameruku Patraine!" for royal-tier spells. Her fairy partner is Mimi, and her crystal ball is a blue diamond.

Her relationships are multifaceted: she teases Doremi yet shares a close bond, offers Hazuki gentle encouragement for her sensitivity, and forms a solid friendship with Onpu after initial distrust over manipulative behavior. She helps Momoko adjust socially and adores the magical baby Hana, often acting protectively. She maintains a rivalry with the wizard world's Leon, whom she finds irritating despite consistently defeating him in sports. An old friend, Kenichi, reappears claiming a childhood marriage promise she made to hide her inability to swim; she cares for him but lacks romantic feelings.

Her design features tan skin, deep blue eyes, and short, flared blue hair with exposed bangs and distinctive curls. She initially wears blue denim overalls over a green shirt, later switching to a green T-shirt, khaki vest, and teal jeans, frequently placing her hands inside her overall bib rather than pockets.

In localization, her favorite food changes from takoyaki to biscuits or cookies. Her role raising Hana showcases her maternal side, though she worries about being less nurturing than her friends. Across seasons, she evolves from a sporty transfer student to a resilient figure balancing humor with emotional depth, consistently using her strengths to support others while confronting personal insecurities.