Prime Minister Fumimaro Konoe asked Aoki to become deputy director of the Cabinet Planning Board in 1937, and he became its chairman in 1939.

After the fall of the Abe administration, Aoki was assigned as a special envoy to the Reorganized National Government of China to guide economic policy.

Aoki visited Japanese-occupied Batavia in May 1943, meeting with Mohammad Hatta, who as representative for the Indonesian nationalists, advised him that unless there was a shift in Japanese policy towards granting independence for Indonesia (as it had for Burma and the Philippines), it would be increasingly difficult to maintain popular support for Japan.

Aoki promised to raise the issue with Tōjō, who mentioned his intent to grant independence to Malaya, Sumatra, Java, Borneo and Sulawesi within a year in his June 1943 parliamentary speech.

[1] After the surrender of Japan, Aoki was arrested (as were all former government members) by the Supreme Commander of the Allied Powers and held in Sugamo Prison on charges of war crimes.