Tokyo, officially Tokyo Metropolis, one of the 47 prefectures of Japan, has served as the Japanese capital since 1869. As of 2014, the Greater Tokyo Arearanked as the most populous metropolitan area in the world. The urban area houses the seat of the Emperor of Japan, of the Japanese government and of the National Diet. Tokyo forms part of the Kantō region on the southeastern side of Japan's main island, Honshu, and includes the Izu Islands and Ogasawara Islands. Tokyo was formerly named Edo when Shōgun Tokugawa Ieyasu made the city his headquarters in 1603. It became the capital after Emperor Meiji moved his seat to the city from Kyoto in 1868; at that time Edo was renamed Tokyo. Tokyo Metropolis formed in 1943 from the merger of the former Tokyo Prefecture  and the city of Tokyo. Tokyo is often referred to as a city but is officially known and governed as a "metropolitan prefecture", which differs from and combines elements of a city and a prefecture, a characteristic unique to Tokyo.

The 23 Special Wards of Tokyo were formerly Tokyo City. On July 1, 1943, it merged with Tokyo Prefecture and became Tokyo Metropolis with an additional 26 municipalities in the western part of the prefecture, and the Izu islandsand Ogasawara islands south of Tokyo. The population of the special wards is over 9 million people, with the total population of Tokyo Metropolis exceeding 13.8 million. The prefecture is part of the world's most populous metropolitan area called the Greater Tokyo Area with over 38 million people and the world's largest urban agglomeration economy. As of 2011, Tokyo hosted 51 of the Fortune Global 500 companies, the highest number of any city in the world at that time. Tokyo ranked third (twice) in the International Financial Centres Development Index. The city is home to various television networks such as Fuji TV, Tokyo MX, TV Tokyo, TV Asahi, Nippon Television, NHK and the Tokyo Broadcasting System.

Nagoya is the largest city in the Chūbu region of Japan. It is Japan's fourth-largest incorporated city and the third-most-populous urban area. It is located on the Pacific coast on central Honshu. It is the capital of Aichi Prefectureand is one of Japan's major ports along with those of Tokyo, Osaka, Kobe, Yokohama, Chiba, and Kitakyushu. It is also the center of Japan's third-largest metropolitan region, known as the Chūkyō metropolitan area. As of 2015, 2.28 million people lived in the city, part of Chūkyō Metropolitan Area's 10.11 million people. It is also one of the 50 largest urban areas in the world.

Osaka is a designated city in the Kansai regionof Japan. It is the capital city of Osaka Prefecture and the largest component of the Keihanshin Metropolitan Area, the second largest metropolitan area in Japan and among the largest in the world with over 19 million inhabitants. Osaka will host Expo 2025. The current mayor of Osaka is Hirohumi Yoshimura.

Nagasaki is the capital and the largest city of Nagasaki Prefecture on the island of Kyushu in Japan. The city's name means "long cape" in Japanese. Nagasaki became a centre of colonial Portuguese and Dutch influence in the 16th through 19th centuries, and the Hidden Christian Sites in the Nagasaki Region have been recognized and included in the UNESCO World Heritage List. Part of Nagasaki was home to a major Imperial Japanese Navy base during the First Sino-Japanese War and Russo-Japanese War.

During World War II, the American atomic bombings of Hiroshima and Nagasaki made Nagasaki the second and, to date, last city in the world to experience a nuclear attack (at 11:02 a.m., August 9, 1945 'Japan Standard Time (UTC+9)').

As of 1 March 2017, the city has an estimated population of 425,723 and a population density of 1,000 people per km2. The total area is 406.35 km2 (156.89 sq mi).