Mitsubishi was the first and largest series producer of Japanese engines during World War II, with a 1937 Pratt & Whitney arrangement possibly contributing to this success. The Kasei (Mars) was the largest of the manufacturer’s original 14-cylinder radials, and was widely used in various models. Between 1941 and 1945, a total of 9,323 engines of all models of Kasei 20 series were manufactured.

The Kasei 25 incorporated a two-speed supercharger, similar to earlier Kasei 21 and 22 models. It was used in a number of war time aircraft including: 1,133 B6N2 Nakajima Tenzan (Heavenly Mountain) (Allied Code Name Jill) single engine, torpedo-bombers; less than 100 of the night fighter version of the Yokosuka P1Y2 Ginga (Milky Way) (Allied Code Name Frances); two prototypes of the four-engine Kawanishi H8K4 maritime reconnaissance flying-boat; and 1,154 twin-engine Mitsubishi G4M2 (Allied Code Name Betty) attack bombers.