My Neighbor Totoro (1988) Anime Watch

Totoro is a forest spirit that little Mei, and later her older sister Satsuki, encounter in a giant camphor tree near their new home in the countryside. Although their father, a university professor, is with them when they move, their mother is in the hospital, recovering from some unnamed illness. When Mei hears that her mother's condition may be getting worse, she resolves to visit her all by herself. When everyone realizes she's missing, only Totoro knows how to find her!