Kameo Ōya was born in the village of Ueno (now part of Yayoi District, Saiki), Ōita Prefecture, Japan, on 12 February 1907. He spent most of his life working in agriculture, cultivating rice and shiitake mushrooms.
In 2004, he entered an assisted living facility for the elderly. Until the age of 105, he rode his bicycle back and forth between his home and rice fields. At the age of 108, he could still read without glasses and walk unassisted. He enjoyed reading, especially books about agriculture and food, and even at the age of 110 he dreamed of building a farm and growing vegetables and herbs.
On 10 May 2015, following the death of 108-year-old Setsuo Ojima of Ōita City, he became the oldest living man in Ōita Prefecture, at the age of 108.
On 25 August 2016, following the death of 114-year-old Mitsue Toyoda, he became the oldest living person in Ōita Prefecture, at the age of 109.
On 2 October 2017, at the age of 110 years, 232 days, he surpassed the final age of Hajime Fujita (1902–2012), becoming the oldest man ever in Ōita Prefecture. In February 2018, he became the first man in Ōita Prefecture to reach the age of 111.
Upon his death, the anonymous lady from Hiji (who was 2 days younger than Ōya) became the oldest living person in the Prefecture, and Goro Danjo succeeded him as the oldest living man in the Prefecture.