What was the planned Allied invasion of Honshu called after Operation Olympic?

The planned Allied invasion of Honshu was called Operation Coronet.

Operation Coronet was the second major phase of Operation Downfall, the projected Allied invasion of Japan. It was intended to follow Operation Olympic, which would have seized southern Kyushu. Coronet would then have attacked Honshu, Japan’s largest island, with the principal objective centered on the Kanto Plain near Tokyo.

Planners scheduled Coronet for March 1, 1946. The plan called for a massive force assembled from American and Commonwealth units. Its scale reflected Allied expectations that Japan’s remaining military forces and civilian population might resist a home-island invasion.

Coronet never took place because Japan surrendered in 1945. The codename is commonly mixed up with Olympic, but the distinction is straightforward: Olympic meant Kyushu, while Coronet meant Honshu. Downfall referred to the complete invasion concept rather than to only one landing operation.