In May 1939, Mori was relegated to reserve status. He was recalled to active duty in July 1942 and participated as a fighter pilot in the Solomon Islands and New Guinea campaigns from air bases at Rabaul and Buin. Between October 1942 and May 1943, Mori was credited with shooting down five enemy aircraft.
In May 1943, Mori returned to Japan and served as a test pilot with the IJN"s Naval Air Technology Arsenal until his retirement in August 1944.
Mori died of illness in 1960.