During the Second Sino-Japanese War, Akinaga was chief of the Maneuvers Section of 6th Division between 1937–1938 and was active at the Battle of Nanking and the Battle of Wuhan. In July 1938, he was promoted to colonel. In December of the same year, following the Battle of Lake Khasan against the Soviet Union, Akinaga was given command of the IJA 75th Regiment where he served until 1940. Akinaga was appointed chief of staff of 13th Division, stationed in China at the start of the Pacific War. Akinaga was promoted to major general in August 1941 and in August 1942 was appointed commanding officer of the Infantry Group of 57th Division stationed in Manchukuo.