In 1947 after the end of the Second Sino-Japanese War, Sano's family returned to Yamanashi Prefecture in Japan, where she initially stayed with her paternal uncle.
In 1977, Sano published her most well known picture book, The Cat Who Lived a Million Times, which became a domestic and international best-seller.
Throughout her career, Sano also produced illustrations for others’ works, translated foreign picture books into Japanese, wrote screenplays, and published novels.
Her script Jitensha buta ga yatte kita (The Bicycle Pig Is Coming, 1987) was used in stage performances for children by the Maru Theater Company.
Among other collaborative work, she illustrated a volume of Shuntarō Tanikawa's poems, Onna Ni (Floating the River in Melancholy), which was translated into English by William I. Eliott and Kazuo Kawamura and won the American Book Award in 1989.
In her essay collection Useless Days (published in 2006), Sano confessed that she had only two years left to live due to her cancer.
[9] In 2012, a documentary, The Cat that Lived a Million Times (ドキュメンタリー映画 100万回生きたねこ, 100 Mankai Ikita Neko) was released, taking its name from Sano's popular 1977 children's book.
[11] In 2014, Yoko-san no Kotoba, a picture book-style introduction to Sano's essays, was produced and broadcast on NHK's One Seg 2 and Educational TV channels.