Miyao Mashima was born in Ueda City, Nagano Prefecture, Japan, on 1 July 1910. She grew up in the Koizumi district of Ueda City, but her parents passed away when she was very young. In 1936, at the age of 25/26, she got married. The couple farmed and raised four sons. She continued to live in Ueda City for the rest of her life.
Mashima passed away of natural causes at her home in Ueda City, Nagano Prefecture, Japan, on 7 April 2023, at the age of 112 years, 280 days.
Following the death of Shizu Sato on 29 August 2020, she became the oldest living person in Nagano Prefecture, Japan.
On 23 March 2023, at the age of 112 years, 265 days, she surpassed Shizu Sato’s final age, becoming the second-oldest person ever in Nagano Prefecture, after Michiko Yamazaki.
Her age was verified by Japan’s MHLW, Ryohei Asano and Yumi Yamamoto, and validated by LongeviQuest on 13 April 2023.