Oikawa was born in Iwate Prefecture on 20 February 1889. In her 20s, she married Ritaro Oikawa and the couple opened and ran an inn together.
Oikawa was widowed shortly after the end of World War I; she ran the inn and raised her three children independently.
As a centenarian, Oikawa enjoyed trips to hot springs, which was a lifelong hobby of hers. In March 1999, she became the longevity recordholder of Iwate Prefecture after surpassing the age of Seki Kitamura.
Towards the end of 2000, Oikawa was hospitalised with pneumonia, later being discharged in July 2001. According to her family, she was strict, but dedicated and hardworking.
Oikawa died of acute heart failure in Ofunato, Iwate, on 3 January 2002 at the age of 112 years, 317 days. She was believed to be Japan’s second-oldest resident after Kamato Hongo, but due to Hongo’s claimed age being called into question, she is now regarded as Japan’s oldest living person from August 2001 until her death. Her Iwate longevity record was broken by Tae Ito in May 2016.