Who are the little Japanese girls who find Totoro?

In 1950s Japan, university professor Tatsuo Kusakabe and his daughters Satsuki and Mei (approximately ten and four years old, respectively) move into an old house close to the hospital where the girls' mother Yasuko is recovering from a long-term illness. The house is inhabited by small, dark, dust-like house spirits called susuwatari, which can be seen when moving from bright places to dark ones.[note 1] When the girls become comfortable in their new house, the susuwatari leave to find another empty house. Mei later discovers two small spirits who lead her into the hollow of a large camphor tree. She befriends a larger spirit, which identifies itself using a series of roars she interprets as "Totoro". Mei thinks Totoro is the troll from her illustrated book Three Billy Goats Gruff, with her mispronouncing troll. Mei falls asleep atop Totoro but when Satsuki finds her, she is on the ground. Despite many attempts, Mei cannot show her family Totoro's tree. Tatsuo comforts her by telling her Totoro will reveal himself when he wants to.

Mei and Satsuki are the two Japanese girls who discover Totoro in the famous Japanese anime My Neighbour Totoro.