Born in Hiroshima, Kaya graduated from Tokyo Imperial University and joined the Ministry of Finance.

Paroled in 1955, Kaya was rehabilitated and served in the House of Representatives for the Liberal Democratic Party, and as Minister of Justice under Hayato Ikeda.

[1] Kaya attended the prestigious First Higher School in Tokyo where he was classmates with Jōtarō Kawakami, who became a socialist leader later in life.

When Fumimaro Konoe formed his cabinet in June the same year Kaya was selected as Minister of Finance.

[1] Ikeda, who had followed Kishi as prime minister, made Kaya Chairman of the Policy Research Council in 1962.

In the same year he became chairman of the Japan War-Bereaved Families Association, a position he held until his death.