The specifics of the exercise are still unknown, but they will be jointly coordinated by the national and prefectural governments. It will be the first time since World War II that such an exercise has been carried out in a major city, although smaller Japanese towns have held similar exercises in the past.
While some Japanese leaders have called for such drills in every major city, civic groups have been trepidatious, fearing alarming the public and hurting the economy.
On December 1, the city of Fukuoka, with 1.6 million residents, became the first major city in Japan to conduct a drill for a possible ballistic missile launch, with phone alerts sent to residents instructing them to head indoors and underground.
Japanese Prime Minister Shinzo Abe has called on prefectural governments to identify facilities and buildings that are sturdy enough to withstand a missile and designate them as emergency shelters.
The megacity of Tokyo — with 13.6 million citizens in the city proper and 37.8 million in its metropolitan area — contains by itself about 30 percent of the Japanese population. It is by far the largest city in Japan and one of the largest in the world.
With such a high population concentration, casualties would likely be extreme were the city to come under attack. In October, the US-Korea Institute at Johns Hopkins University published a study that a single North Korean warhead with a 250 kiloton airburst over Tokyo's city center would lead to 700,000 deaths. By comparison, between 80,000 and 130,000 Tokyo residents perished in the American firebombing of the city during World War II, according to History.com.
The area is also a center for military power. The US Navy deploys a carrier strike group, which includes three cruisers and nine destroyers, out of the Yokosuka Naval Base just 40 miles south of Tokyo, while the US Air Force deploys the bulk of their air power in the region from the Yokota Air Base, also in the Tokyo Metropolitan Area.
"The average Japanese person does not want to think about the worst-case scenario because it is simply too unpleasant, but we cannot keep our heads in the sand any longer," human rights activist Ken Kato told the Telegraph.
"Evacuation drills are a sensible precaution that would help to minimize casualties, in much the same way as we practice what to do in the event of a major earthquake," he observed.
Twice this year, North Korea has test-launched a missile that passed over Japanese territory. Their most recent launch, which took place November 28, fell into the Sea of Japan without passing over Japanese territory.
In July, a public service announcement aired on all major networks explaining what citizens should do in the case of a North Korean nuclear strike.