[2][3][4] In the incident, a victimized daughter, Chiyo Aizawa (相沢 チヨ, Aizawa Chiyo)[5][6] (born January 31, 1939) who had been sexually abused by her father for about 15 years, eventually killed him on October 5, 1968.
[5][7] Aizawa's controversial trial led to the repeal of parricide as an offence in the Criminal Code of Japan.
[8] Takeo was an alcoholic and systematically raped his daughter from 1953, when she was fourteen years old, onwards.
Because the family law in Japan forbids polygamy and intermarriage between close relatives but does not forbid inbreeding, a family register recorded Chiyo's children as her father's illegitimate children.
The Utsunomiya District Court considered article 200 unconstitutional and acquitted Aizawa because the crime originated via self-defense on May 29, 1969.
In a final appeal, the Supreme Court of Japan accepted the argument that imposing a harsh penalty on Aizawa would violate the principle of human equality before the law found in the constitution.