Mei Kusakabe, the energetic four-year-old sister of Satsuki, moves with her family to a rural house near her mother's long-term illness hospital. Bursting with youthful curiosity and playful innocence, she discovers small, rabbit-like spirits during her explorations. Following them into a giant camphor tree's hollow, she encounters a large forest spirit. Interpreting its roars as "Totoro," a name borrowed from her *Three Billy Goats Gruff* storybook troll, she experiences her first supernatural encounter.

Her personality blends stubbornness with deep affection for her family. She frequently mimics Satsuki, seeking approval and companionship, and becomes distressed during separations like school hours. This attachment extends to her mother; learning of a postponed hospital visit due to illness complications prompts Mei to impulsively set out alone to deliver fresh corn. This act leads to her becoming lost, sparking a village-wide search. Her vulnerability surfaces vividly through inconsolable tears, especially after a heated argument where Satsuki snaps at her.

Her bond with Totoro deepens from initial discovery into reliance. The spirit appears during moments of distress or boredom—like waiting for her father at a rainy bus stop or participating in a midnight dance that magically sprouts seeds into towering trees. These experiences, whether real or imagined, help her cope with anxiety about her mother's health. By the film's end, Mei shows nascent independence but ultimately strengthens her bond with Satsuki during their reunion after being lost.

A short sequel exclusive to the Ghibli Museum, *Mei and the Kittenbus*, features Mei interacting with a smaller, bus-like feline spirit, though specific plot details remain undocumented. Across her appearances, Mei's journey centers on navigating childhood wonder amid familial stress, finding resilience through imagination and nature.