Onoda was born on March 19, 1922, in Kamekawa Village, Kaisō District, Wakayama Prefecture, Japan. He belonged to a family of ancient samurai warrior class, and his father had been a sergeant in the 4th Cavalry Brigade until 1943, when he was killed in action in China. When he was 17 years old, he went to work for the Tajima Yoko trading company in Wuhan, China. When he was 18, he was enlisted in the Imperial Japanese Army Infantry.