It was conceived as a method for mounting aerial attacks from Japan against industrial targets along the west coast (e.g., San Francisco) and in the Midwest (e.g., Detroit, Milwaukee, Chicago, and Wichita) and the northeast (e.g., New York City and Norfolk) of the United States.
Japan's worsening war situation resulted in the project's cancellation in 1944 and no prototype was ever built.
[1] The Fugaku had its origins in "Project Z (bomber project)", a 1942 Imperial Japanese Army specification for an intercontinental bomber which could take off from the Kuril Islands, bomb the contiguous United States, then continue onward to land in German-occupied France.
[1][2][3] Project Z called for three variations on the airframe: heavy bomber, transport (capable of carrying 300 troops), and a gunship armed with forty downward-firing machine guns in the fuselage for intense ground attacks at the rate of 640 rounds per second (i.e. 38,400 rounds per minute).
[1] Data from Japanese Secret Projects:Experimental aircraft of the IJA and IJN 1939–1945[1]General characteristics Performance Armament