Arrietty, a 14-year-old of the Clock family, belongs to a lineage of miniature Borrowers who discreetly sustain themselves by collecting unnoticed resources from human homes. Measuring four inches tall, she sports auburn hair secured by a red clothespin and dons functional attire like red dresses paired with brown boots during covert supply missions. Her small frame demands ingenuity, transforming mundane items into survival tools—a sewing pin becomes a sword, and human earrings serve as climbing anchors.

Reared under stringent protocols to evade human interaction, Arrietty outwardly complies with her parents’ guarded ethos yet inwardly harbors a bold, curious spirit. Defying caution, she ventures beyond her family’s concealed dwelling for her inaugural solo borrowing task. This expedition leads her to Shō, an ailing human boy recuperating in the house. Against Borrower dogma, she cautiously forges a connection with him, testing long-held fears of human encounters.

When the housekeeper Haru exposes the Clock family’s presence and imprisons Arrietty’s mother Homily, Arrietty confronts mounting perils. Leveraging her knowledge of the house’s architecture and human artifacts, she devises a daring rescue, proving her tactical prowess. The crisis triggers their exodus from a decades-old home. Guided by Spiller, a wandering Borrower, the family flees downstream in an adapted kettle, seeking refuge in uncharted territory.

Through these trials, Arrietty transitions from a protected youth to a decisive leader, harmonizing duty to kin with self-reliant judgment. Her rapport with Shō underscores a mutual, cross-species empathy, bridging divides through trust. Their departure hints at an uncertain future, with the Clocks poised to persist in their clandestine borrowing traditions wherever they next take root.