What area was Operation Coronet planned to invade?

Operation Coronet was planned to invade the Kantō Plain.

Coronet was the second phase of Operation Downfall, the proposed Allied invasion of Japan. Its objective was the Kantō Plain on Honshū, the main Japanese island, near Tokyo. The operation was tentatively scheduled for March 1, 1946, after the planned November 1945 landings in Kyūshū under Operation Olympic.

The Kantō Plain was strategically important because it contained Tokyo and surrounding transportation, industrial, and political centers. The plan called for large American forces to land on beaches including Kujūkuri Beach and near Sagami Bay, then advance inland toward the capital.

Coronet would have followed the establishment of airfields and supply bases in Kyūshū. It was never launched because Japan surrendered in August 1945. The name is sometimes confused with Olympic, but Olympic concerned southern Kyūshū, while Coronet concerned the Kantō region of Honshū.