A Hokkaido man in his 70s plans to file a lawsuit seeking damages from the government over his forced sterilization at around age 20 under the 1948 eugenic protection law, sources said Thursday, as a related investigation unearthed documents showing children aged 15 and below — including one as young as 9 — were also sterilized under the law.

The revelations follow a lawsuit filed against the state by a woman in her 60s in Miyagi Prefecture on Jan. 30, seeking ¥11 million in damages over her forced sterilization when she was a teenager.

Japan's now-defunct eugenic protection law authorized the sterilization of people with mental disabilities and illness or hereditary disorders to prevent births of what were feared would be "inferior" offspring. It also allowed for forcible abortions without the consent of the individuals or their relatives.