Kotoe Nishikawa was born in Tamba-Sasayama, Hyōgo Prefecture, Japan, on 28 October 1913. She was the youngest among five siblings and had four older brothers. Her eldest brother was 18 years her senior and took great care of her. According to her family, in her youth, she was more energetic than other girls. At some point during her teenage years, she moved to Tokyo to work as an assistant nurse.

At the age of 24, she married, resigned from her job, and relocated to Hirakata City in Osaka Prefecture. Throughout World War II, whenever the air raid siren sounded, she sought refuge in an air raid shelter with her five children, all aged between 0 and 7. Although they survived the war, her house was destroyed during the Osaka Air Raid. Following the conclusion of World War II, she and her family moved to Sakai City, where, at the age of 36, she gave birth to her youngest child.

After her children became independent and grandchildren were born, her purpose in life shifted to babysitting her grandchildren. Around the age of 80, she devoted herself to caring for approximately 15 grandchildren. Her family stated that her experience as an assistant nurse before marriage and her dedication were deeply ingrained in her, prompting her to also care for relatives when they fell ill. In her 80s, she fractured her right femur, prompting her to start utilizing daycare services. At the age of 90, she broke her left femur, following which she moved into a nursing home. Bolts were placed in both femurs, but she retained the ability to walk independently until she was about 100 years old. She loves to read kanji. She was able to read difficult kanji that ordinary people have a hard time reading.

At the age of 110, she eats three full meals a day and is doing well. Her family praised her as “a person who is devoted to others.” Her mother lived to be around 95 years old, and her siblings lived to be over 80 years old. Five of her six children are still alive as of November 2023.