Mitsue Toyoda was born in Japan on 15 February 1902. In June 1999, she moved to the nursing home Yamakaen [Japanese: 山香苑] in Yamagamachi, Kitsuki City.
Following the death of 108-year-old Kazue Inamori on 7 November 2009, Toyoda became the oldest living person in Oita Prefecture, a title she held jointly with Hajime Fujita until his death on 3 October 2012.
In October 2011, Toyoda was reported to be an energic grandmother. In September 2014, she was visited by the governor of Oita Prefecture. At the time, she was reported to have bad hearing, and to have declining eyesight, but to eat without assistance.
Mitsue Toyoda died in Kitsuki City, Oita Prefecture, Japan, on 25 August 2016. At the time of her death, she was the sixth-oldest living verified person in the world. Next to Yukie Hino, she was the penultimate Japanese person to have been born in 1902. Following her death, then 109-year-old Kameo Oya became the oldest living person in Oita Prefecture.