The family moved to New York City in 1940. The next year, Eisuke was transferred from New York City to Hanoi, and the family returned to Japan. Ono was enrolled in Keimei Gakuen, an exclusive Christian primary school run by the Mitsui family. She remained in Tokyo throughout World War II and the great fire-bombing of March 9, 1945, during which she was sheltered with other family members in a special bunker in Tokyo's Azabu district, away from the heavy bombing. Ono later went to the Karuizawa mountain resort with members of her family.