The Japanese never considered an invasion of Hawaii in December 1941
During the planning phase for the Pearl Harbor attack, at several junctures the subject of invasion of the Hawaiian Islands arose. As late as September 1941, a proposal was put forth to invade using two divisions of troops, approximately 30,000 men, supported by the carrier strike force and an invasion fleet of about 75-80 ships. Minoru Genda, chief planner for the attack, supported the idea of invasion, believing that occupation of the Hawaiian Islands by the Japanese would force the Americans to sue for peace. Japanese forces in Hawaii threatened the West Coast of the United States, as well as the Panama Canal after America lost most if not all of its Pacific Fleet. Genda went so far as to recommend invasion of Hawaii rather than the Philippines. Preliminary studies indicated it would take the Japanese roughly one month to secure the islands following the initial raids.
In the Japanese military hierarchy, the Imperial Japanese Army (IJA) held sway over their seagoing counterparts. The Army opposed the invasion of Hawaii, largely because it diverted resources from their desired push to the south and east. Japanese war plans of the 1920s and 1930s focused on the seizure of the Philippines, removing the American presence from the Southwest Pacific and providing the Japanese with airbases and naval installations which threatened Australia and New Zealand. The Japanese Navy never formally approached the IJA with plans for an invasion, but private discussions soon indicated the Army would not support the idea. Too many of its resources were already tied up in China or committed to the Philippine Campaign. Whether an invasion of Hawaii would have succeeded remains a source of discussion among theorists and alternative history buffs.