The San'yō Main Line (山陽本線, San'yō-honsen) is a major railway line owned by JR Group companies in western Japan, connecting Kōbe Station and Moji Station, largely paralleling the coast of the Seto Inland Sea, in other words, the southern coast of western Honshu. The San'yō Shinkansen line largely parallels its route. The name Sanyō derived from the ancient region and highway San'yōdō, the road on the sunny (south) side of the mountains.
The Sanyō Main Line is operated by two JR companies:
The Taiheiyō Belt (Japanese: 太平洋ベルト, Hepburn: Taiheiyō Beruto; lit. "Pacific Belt"), also known as the Tōkaidō corridor, is the megalopolis in Japan extending from Ibaraki Prefecture in the northeast to Fukuoka Prefecture in the southwest, running for almost 1,200 km (750 mi). Its estimated population as of 2011 was about 80 million.
The urbanization zone runs mainly along the Pacific coast (hence the name) of Japan from Kantō region to Osaka, and the Inland Sea (on both sides) to Fukuoka, and is concentrated along the Tōkaidō–Sanyō rail corridor. A view of Japan at night clearly shows a rather dense and continuous strip of light (demarcating urban zones) that delineates the region. The high population is particularly due to the large plains – the Kantō Plain, Kinai Plain, and Nōbi Plain – which facilitate building in otherwise mountainous Japan.
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.