Olga Tolstaya

Olga Tolstoy is the 15-year-old daughter of the Russian hero Ivan Tolstoy and former professional ballerina Emilia Tolstaya. She is a huge fan of Hibito and befriends him during his stay in Russia. Olga tries to act like an adult and puts on a poker face (especially in front of Hibito) despite being only 15.

(Source: Uchuu Kyoudai Wikia)