Shy sixth-grader Akane Uesugi finds expressing her feelings difficult. On the eve of her birthday, her mother sends her to collect a present from aunt Chii's antique shop. There, she stumbles upon alchemist Hippocrates and his fairy apprentice Pipo, emerging from the basement. Hippocrates declares her the prophesied "Green Goddess," destined to save their world. Passing through the basement door, Akane enters the parallel realm of "The World Beyond" or "Wonderland." This world suffers environmental collapse: rivers run dry and trees fade to grey. Akane learns the water cycle is broken because the prince who maintains it through the "Ritual of Droplet Cutting" has vanished. Tasked as savior, her mission is to find the missing prince, restore balance, and halt the decay. She journeys with aunt Chii, Hippocrates, and Pipo, facing obstacles including the antagonist Zan Gu who opposes them. Doubtful of her own abilities and hesitant to accept responsibility, Akane evolves during her Wonderland experiences. Her challenges include navigating strange landscapes, encountering fantastical beings like oversized sheep, and reconciling her insecurities with the legend's expectations. Each challenge chips away at her uncertainty, demanding decisions that forge her resilience and sense of agency. Details about her family beyond her mother Midori and aunt Chii, or her life before the antique shop, are not specified. Physical descriptions note only common traits for a preadolescent Japanese girl. Her complete story arc resolves within the film, focusing on resolving Wonderland's crisis and the personal growth gained through her quest.