Mint serves as princess of the World of Dreams and Magic, a realm whose landscapes mirror Earth's hopes and dreams. This world decays as humans abandon their dreams, inviting darkness to corrupt hearts and wither magic. Witnessing her rainbow garden's flowers turn blue—a symbol of spreading sorrow—on her twelfth birthday, Mint resolves to travel to Earth. Her mission: reignite human hopes and dreams to prove her worth as a future ruler.

She balances kindness and gentleness with tomboyish energy and flashes of selfishness. Standing 147 cm (4'10"), Mint displays an insatiable appetite, devouring hamburgers, fries, cookies, and snacks at all hours, and possesses zero sense of direction. Her magical tools include the Mint Stick wand, Mint Compact (an arm attachment transforming into wand or arrow), Mint Arrow for outfit changes, Star Accessory Earrings, and a Star Necklace. Her transformation phrase is "Parieru Remurin Sweet Mint."

Accompanied by Waffle, her flying penguin companion, Mint lives on Earth with Aunt Herb at the "Happy Shop" gift store. She befriends two humans: Plum, a resourceful boy prone to vertigo who aids her early struggles, and Nut, a book-loving fourteen-year-old devoted to family. Both receive magical items—Plum a pendant, Nut a synthesizer brooch—and learn Mint's secret identity.

Mint tackles human anxieties, family strife, and puberty with her magic, though initial power mishaps cause chaos. Ordered home after her mission, she defies orders to stay when Plum faces a medical crisis. By magically transporting an ambulance through blocked streets to save him, she discovers magic's true purpose: selfless compassion. This act instantly restores the rainbow garden's flowers, confirming her maturity and readiness to rule.