Gunma Prefecture in the context of "Nagano Prefecture"

The Greater Tokyo Area is the most populous metropolitan area in the world, consisting of the Kantō region of Japan (including Tokyo Metropolis and the prefectures of Chiba, Gunma, Ibaraki, Kanagawa, Saitama, and Tochigi) as well as the prefecture of Yamanashi of the neighboring Chūbu region. In Japanese, it is referred to by various terms, one of the most common being Capital Region (首都圏, Shuto-ken).

As of 2016, the United Nations estimates the total population at 38,140,000. It covers an area of approximately 13,500 km (5,200 mi), giving it a population density of 2,642 people/km. It is the second-largest single metropolitan area in the world in terms of built-up or urban function landmass at 8,547 km (3,300 mi), behind only the New York City metropolitan area at 11,642 km (4,495 mi). With over US$2 trillion in GDP, Tokyo remains the second-largest metropolitan economy in the world, also behind New York.

The Kantō region (関東地方, Kantō Chihō; IPA: [kaꜜn.toː, kan.toː tɕiꜜ.hoː, kan.toː tɕi̥.hoꜜː]) is a geographical region of Honshu, the largest island of Japan. In a common definition, the region includes the Greater Tokyo Area and encompasses seven prefectures: Chiba, Gunma, Ibaraki, Kanagawa, Saitama, Tochigi, and Tokyo. Slightly more than 45 percent of the land area within its boundaries is the Kantō Plain. The rest consists of the hills and mountains that form land borders with other regions of Japan.

As the Kantō region contains Tokyo, the capital and largest city of Japan, the region is considered the center of Japan's politics and economy. According to the official census on October 1, 2010, by the Statistics Bureau of Japan, the population was 42,607,376, amounting to approximately one third of the total population of Japan.

Saitama Prefecture (埼玉県, Saitama-ken; Japanese pronunciation: [saꜜi.ta.ma, sai.ta.maꜜ.keɴ]) is a landlocked prefecture of Japan located in the Kantō region of Honshu. Saitama Prefecture has a population of 7,338,536 (January 1, 2020) and has a geographic area of 3,797 km (1,466 sq mi). Saitama Prefecture borders Tochigi Prefecture and Gunma Prefecture to the north, Nagano Prefecture to the west, Yamanashi Prefecture to the southwest, Tokyo to the south, Chiba Prefecture to the southeast, and Ibaraki Prefecture to the northeast.

Saitama is the capital and largest city of Saitama Prefecture, with other major cities including Kawaguchi, Kawagoe, and Tokorozawa.

Tochigi Prefecture (栃木県, Tochigi-ken) is a landlocked prefecture of Japan located in the Kantō region of Honshu. Tochigi Prefecture has a population of 1,897,649 (1 June 2023) and has a geographic area of 6,408 km (2,474 sq mi). Tochigi Prefecture borders Fukushima Prefecture to the north, Gunma Prefecture to the west, Saitama Prefecture to the south, and Ibaraki Prefecture to the southeast.

Utsunomiya is the capital and largest city of Tochigi Prefecture, with other major cities including Oyama, Tochigi, and Ashikaga. Tochigi Prefecture is one of only eight landlocked prefectures and its mountainous northern region is a popular tourist region in Japan. The Nasu area is known for its onsens, local sake, and ski resorts, the villa of the Imperial Family, and the Nasushiobara station of the Shinkansen railway line. The city of Nikkō, with its ancient Shintō shrines and Buddhist temples, is a UNESCO World Heritage Site.

36°00′N 140°00′E / 36.000°N 140.000°E / 36.000; 140.000

The Kantō Plain (Japanese: 関東平野, Hepburn: Kantō heiya), in the Kantō region of central Honshu, is the largest plain in Japan. Its 17,000 km covers more than half of the region extending over Tokyo, Saitama Prefecture, Kanagawa Prefecture, Chiba Prefecture, Gunma Prefecture, Tochigi Prefecture, and Ibaraki Prefecture.

The Northeastern Japan Arc, also Northeastern Honshū Arc, is an island arc on the Pacific Ring of Fire. The arc runs north to south along the Tōhoku region of Honshū, Japan. It is the result of the subduction of the Pacific plate underneath the Okhotsk plate at the Japan Trench. The southern end of the arc converges with the Southwestern Japan Arc and the Izu–Bonin–Mariana Arc at the Fossa Magna (ja) at the east end of the Itoigawa-Shizuoka Tectonic Line (ITIL). This is the geologic border between eastern and western Honshū. Mount Fuji is at the point where these three arcs meet. To the north, the Northeastern Japan arc extends through the Oshima Peninsula of Hokkaidō. The arc converges in a collision zone with the Sakhalin Island Arc and the Kuril Island Arc in the volcanic Ishikari Mountains of central Hokkaidō. This collision formed the Teshio and Yūbari Mountains.

The Ōu Mountains form the backbone of the volcanic part of the inner arc that run from Natsudomari Peninsula in Aomori Prefecture south to Mount Nikkō-Shirane in Tochigi and Gunma prefectures. The volcanic front consists of four north to south lines of Quaternary volcanoes and calderas, which extend the length of the range. It also includes the Quaternary volcanoes of southwestern Hokkaido. The Dewa Mountains and the Iide Mountains are non-volcanic uplift ranges that run parallel to the west of the Ōu Mountains.

Niigata Prefecture (新潟県, Niigata-ken; Japanese pronunciation: [ɲiː.ɡa.ta, -taꜜ.keɴ, ɲiː.ŋa-]) is a prefecture in the Chūbu region of Honshu of Japan. Niigata Prefecture has a population of 2071066 (1 October,2025) and is the fifth-largest prefecture of Japan by geographic area at 12,584.18 km (4,858.78 sq mi). Niigata Prefecture borders Toyama Prefecture and Nagano Prefecture to the southwest, Gunma Prefecture to the south, Fukushima Prefecture to the east, and Yamagata Prefecture to the northeast.

Niigata is the capital and largest city of Niigata Prefecture, with other major cities including Nagaoka, Jōetsu, and Sanjō. Niigata Prefecture contains the Niigata Major Metropolitan Area centered on Niigata with a population of 1,395,612, the largest metropolitan area on the Sea of Japan coast and the twelfth-largest in Japan. Niigata Prefecture is part of the historic Hokuriku region and features Sado Island, the sixth largest island of Japan in area following the four main islands and Okinawa Island.

Fukushima Prefecture (福島県, Fukushima-ken; Japanese pronunciation: [ɸɯ̥.kɯꜜ.ɕi.ma, -kɯ.ɕi.maꜜ.keɴ]) is a prefecture of Japan located in the Tōhoku region of Honshu. Fukushima Prefecture has a population of 1,771,100 (as of 1 July 2023) and has a geographic area of 13,783.90 square kilometres (5,321.99 sq mi). Fukushima Prefecture borders Miyagi Prefecture and Yamagata Prefecture to the north, Niigata Prefecture to the west, Gunma Prefecture to the southwest, and Tochigi Prefecture and Ibaraki Prefecture to the south.

Fukushima is the capital and Iwaki is the largest city of Fukushima Prefecture, with other major cities including Kōriyama, Aizuwakamatsu, and Sukagawa. Fukushima Prefecture is located on Japan's eastern Pacific coast at the southernmost part of the Tōhoku region, and is home to Lake Inawashiro, the fourth-largest lake in Japan. Fukushima Prefecture is the third-largest prefecture of Japan (after Hokkaido and Iwate Prefecture) and divided by mountain ranges into the three regions of Aizu, Nakadōri, and Hamadōri.