Shikoku in the context of "Okinawa Prefecture"

Japan is often divided into regions, each containing one or more of the country's 47 prefectures at large. Sometimes, they are referred to as "blocs" (ブロック, burokku), or "regional blocs" (地域ブロック, chiiki burokku) as opposed to more granular regional divisions. They are not official administrative units, though they have been used by government officials for statistical and other purposes since 1905. They are widely used in, for example, maps, geography textbooks, and weather reports, and many businesses and institutions use their home regions in their names as well, for example Kyushu National Museum, Kinki Nippon Railway, Chūgoku Bank, and Tōhoku University.

One common division groups the prefectures into eight regions. In this arrangement, of the four main islands of Japan, Hokkaidō, Honshu, Shikoku, and Kyūshū, each form their own region, with Kyūshū also including the Satsunan Islands. The largest island, Honshū, is split into five regions. Okinawa Prefecture is usually considered part of Kyūshū, but it is sometimes treated as its own ninth region.

Japan is an archipelagic country comprising a stratovolcanic archipelago over 3,000 km (1,900 mi) along the Pacific coast of East Asia. It consists of 14,125 islands. The five main islands are Hokkaido, Honshu, Kyushu, Shikoku, and Okinawa. The other 14,120 islands are classified as "remote islands" by the Japanese government. The Ryukyu Islands and Nanpō Islands are south and east of the main islands.

The territory covers 377,973.89 km (145,936.53 sq mi). It is the fourth-largest island country in the world and the largest island country in East Asia. The country has the 6th longest coastline at 29,751 km (18,486 mi) and the 8th largest Exclusive Economic Zone of 4,470,000 km (1,730,000 sq mi) in the world.

The Philippine Sea is a marginal sea of the Western Pacific Ocean east of the Philippine Archipelago and the largest sea in the world, occupying an estimated surface area of 5 million square kilometers (2×10^ sq mi). The Philippine Sea Plate forms the floor of the sea. Its western border is the first island chain to the west, comprising the Ryukyu Islands in the northwest and Taiwan in the west. Its southwestern border comprises the Philippine islands of Luzon, Catanduanes, Samar, Leyte, and Mindanao. Its northern border comprises the Japanese islands of Honshu, Shikoku and Kyūshū. Its eastern border is the second island chain to the east, comprising the Bonin Islands and Iwo Jima in the northeast, the Mariana Islands (including Guam, Saipan, and Tinian) in the due east, and Halmahera, Palau, Yap and Ulithi (of the Caroline Islands) in the southeast. Its southern border is Indonesia's Morotai Island.

The sea has a complex and diverse undersea relief. The floor is formed into a structural basin by a series of geologic faults and fracture zones. Island arcs, which are actually extended ridges protruding above the ocean surface due to plate tectonic activity in the area, enclose the Philippine Sea to the north, east and south. The Philippine archipelago, Ryukyu Islands, and the Marianas are examples. Another prominent feature of the Philippine Sea is the presence of deep sea trenches, among them the Philippine Trench and the Mariana Trench, containing the deepest point on the planet.

The Tosa Domain (土佐藩, Tosa-han) was a feudal domain under the Tokugawa shogunate of Edo period Japan, controlling all of Tosa Province in what is now Kōchi Prefecture on the island of Shikoku. It was centered around Kōchi Castle, and was ruled throughout its history by the tozama daimyō Yamauchi clan. Many people from the domain played important roles in events of the late Edo period including Nakahama Manjirō, Sakamoto Ryōma, Yui Mitsue, Gotō Shōjirō, Itagaki Taisuke, Nakae Chōmin, and Takechi Hanpeita. Tosa Domain was renamed Kōchi Domain (高知藩, Kōchi-han) during the early Meiji period until it was dissolved in the abolition of the han system in 1871 and became Kōchi Prefecture.

Japanese people (Japanese: 日本人, Hepburn: Nihonjin; IPA: [ɲihoɲdʑiꜜɴ]) are an East Asian ethnic group native to the Japanese archipelago. Japanese people constitute 97.1% of the population of the country of Japan. Worldwide, approximately 125 million people are of Japanese descent, making them one of the largest ethnic groups. Approximately 119.9 million Japanese people are residents of Japan, and there are approximately five million members of the Japanese diaspora, known as Nikkeijin (日系人).

In some contexts, the term "Japanese people" might be used to refer specifically to the Yamato people, who are primarily from the historically principal islands of Honshu, Kyushu and Shikoku and constitute by far the largest group. In other contexts, the term could include other groups native to the Japanese archipelago, including Ryukyuan people, who share connections with the Yamato but are often regarded as distinct, and Ainu people. In recent decades, there has also been an increase in the number of people with both Japanese and non-Japanese roots, including those who are half Japanese.

Wakayama Prefecture (和歌山県, Wakayama-ken; Japanese pronunciation: [wa.kaꜜ.ja.ma, wa.ka.ja.maꜜ.keɴ]) is a prefecture of Japan located in the Kansai region of Honshu. Wakayama Prefecture has a population of 876,030 (as of 1 February 2025) and a geographic area of 4,724 square kilometres (1,824 sq mi). Wakayama Prefecture borders Osaka Prefecture to the north, and Mie Prefecture and Nara Prefecture to the northeast.

Wakayama is the capital and largest city of Wakayama Prefecture, with other major cities including Tanabe, Hashimoto, and Kinokawa. Wakayama Prefecture is located on the southwestern coast of the Kii Peninsula on the Kii Channel, connecting the Pacific Ocean and Seto Inland Sea, across from Tokushima Prefecture on the island of Shikoku.

The Seto Inland Sea (瀬戸内海, Seto Naikai), sometimes shortened to the Inland Sea, is the body of water separating Honshu, Shikoku, and Kyushu, three of the four main islands of Japan. It serves as a waterway connecting the Pacific Ocean to the Sea of Japan. It connects to Osaka Bay and provides a sea transport link to industrial centers in the Kansai region, including Osaka and Kobe. Before the construction of the San'yō Main Line, it was the main transportation link between Kansai and Kyūshū.

Yamaguchi, Hiroshima, Okayama, Hyōgo, Osaka, Wakayama, Kagawa, Ehime, Tokushima, Fukuoka, and Ōita prefectures have coastlines on the Seto Inland Sea; the cities of Hiroshima, Iwakuni, Takamatsu, and Matsuyama are also located on it.

Hiroshima Prefecture (広島県, Hiroshima-ken; Japanese pronunciation: [çi.ɾo.ɕi.ma, -maꜜ.keɴ]) is a prefecture of Japan located in the Chūgoku region of Honshu. Hiroshima Prefecture has a population of 2,811,410 (1 June 2019) and has a geographic area of 8,479 km (3,274 sq mi). Hiroshima Prefecture borders Okayama Prefecture to the east, Tottori Prefecture to the northeast, Shimane Prefecture to the north, and Yamaguchi Prefecture to the southwest. Hiroshima Prefecture also borders Ehime Prefecture for 74 metres (243 ft) on Hyōtanjima.

Hiroshima is the capital and largest city of Hiroshima Prefecture, and the largest city in the Chūgoku region, with other major cities including Fukuyama, Kure, and Higashihiroshima. Hiroshima Prefecture is located on the Seto Inland Sea across from the island of Shikoku, and is bounded to the north by the Chūgoku Mountains. Hiroshima Prefecture is one of the three prefectures of Japan with more than one UNESCO World Heritage Site.