The first full-length animated film by Studio Ghibli was made without the direct involvement of masters Miyazaki and Takahata. The plot of "Marnie" is based on a book by British writer Joan Robinson, which Miyazaki recommended as required reading, so it's not surprising that his studio took on the adaptation.
Anna, an orphaned, withdrawn, and rather rough girl, has a passion for drawing but has no friends. The situation changes when she goes to Hokkaido and meets her peer, Marnie. The girls become friends, but sometimes Anna feels that Marnie is a product of her imagination.
Anna's story is somewhat similar to Chihiro's adventures in "Spirited Away," only here the action unfolds not in the spirit world but in the world of people who are not averse to surrounding themselves with visions. The line between reality and fantasy in Ghibli's plots is very thin.