At the beginning of the film, Mei Kusakabe falls into the tree's roots and enters an opening, where Totoro is sleeping. She becomes curious and sits on his belly, laughing at him as he sneezes in his sleep. When he wakes up, she asks him what his name is, and he yawns, unable to communicate. The sound of his yawn sounds like, 'Totoro', so Mei decides to call him that. Eventually, she falls asleep on Totoro's belly, and when she wakes up, she's found in by Satsuki Kusakabe in an opening near the tree.
Next to the tree there is a Suitengu shrine. In Japanese religion Shinto camphor trees are holy. Japaneses believe Kodamas live there. So they add a rope with papers around the tree to protect it against bad influences.