A high court on Tuesday upheld a lower court ruling that sentenced a former top bureaucrat to six years in prison for murdering his socially reclusive son in Tokyo in 2019.

The Tokyo High Court rejected an appeal by the defense team of Hideaki Kumazawa, 77, former vice minister for agriculture, forestry and fisheries, who pleaded not guilty, claiming he had feared for his life and acted in self-defense against his 44-year-old eldest son, who had a developmental disorder.

The defense team argued that even if the claim of self-defense was rejected, Kumazawa should only have received a suspended sentence.

Presiding Judge Toru Miura denied the claim of self-defense, saying there were no "realistic signs of danger," as the son did not have any weapons at hand and had not appeared to have chased or attacked the defendant.

Although Kumazawa had long supported his son and suffered a violent assault from him six days prior to the stabbing, the initial sentence "cannot be labeled unjust," the judge said.

According to the ruling, on June 1, 2019, Kumazawa stabbed his son Eiichiro multiple times, including in the neck, resulting in death due to massive blood loss.

In December that year, the Tokyo District Court sentenced the former bureaucrat to a six-year prison term, while acknowledging that Kumazawa had suffered violence at the hands of his son.

Kumazawa served as Japan's ambassador to the Czech Republic after retiring from the farm ministry in 2002.

The case has drawn considerable public attention due to the large number of social recluses, known as hikikomori, age 40 to 64 in Japan.