Born in 1940 in Uryū, Hokkaido Prefecture, Japan to a coal-mining family. In 1968, he left for Tokyo, and became familiar with the neighborhood of Sanya. In 1972, he formed a committee aimed at fighting crime there. In 1982, he assisted with the establishment of the National Conference of Day Laborers’ Unions. After the murder of Mitsuo Sato and according to his wishes, Yamaoka began working to complete the film Yama – Attack to Attack. On 13 January 1986, he was shot to death on a street in Shinjuku Ward, Tokyo, by a member of the ultra-nationalist Konryu gang. He was 45 years old.