is an island located in the eastern part of the Sea of Japan, under the jurisdiction of Sado City, Niigata Prefecture, Japan, with a coastline of . In October 2017, Sado Island had a population of 55,212 people. Sado Island covers an area of , and is the second largest island after Okinawa Island outside of the four main islands of Japan, excluding the disputed Southern Kurils. The shortest distance between Sado Island and Honshu is . The highest peak on Sado Island is Mount Kinpoku, with an elevation of .
According to the international consensus, during World War II, the island was the site of forced labor. Around 1,500 Korean laborers were conscripted to work in difficult conditions in mines on the island. The Japanese government and some Japanese scholars deny that they were forced to work. In 2022, Japan filed to add the island to the UNESCO World Heritage Site list, which sparked international and domestic criticism.
Geography
The shape of Sado Island resembles the word ‘work’ (工) in Japanese or the letter ‘S’. The topography of the island can be roughly divided into three parts, the Ōsado range in the north, the Kosado range in the south, and the Kakakura plain with flat terrain in between. The Ōsado range area is higher in altitude, and the highest peak of Sado Island, Mount Kinpoku ( above sea level), is also located in this area. The coastline on the north side of Mount Sado is steep, and is a famous tourist spot, among which the Senkaku Bay is the most famous. The Kosado range has a relatively flatter terrain with Satsuma orange and tea trees growing there. Its highest peak is Mount Ōjiyama, with an elevation of . The Nakakura Plain is a large plain in Japan's outlying islands and is also the agricultural area of Sado Island. On the west side of the Kuninaka Plain is Mano Bay, and on the east side is Ryōtsu Bay. The Kokufugawa River (also reads Konogawa River) flows through the Kuninaka Plain, with a total length of , and flows into Mano Bay. Its watershed area accounts for 20% of Sado Island. Lake Kamo, the largest lake in Niigata Prefecture, is located at the eastern end of the Kuninaka Plain. Lake Kamo was originally a freshwater lake, and later turned into a lagoon after an opening built to the Sea of Japan. Oyster breeding flourishes in the lake. Part of Sado Island belongs to the Sado-Yahiko-Yoneyama Quasi-National Park.
Weather and Climate
Affected by the warm Black Current that passes through the Sado waters, the winter in Sado Island is warmer than that in Niigata Prefecture and with less snow. In summer, due to the influence of ocean, the temperature difference between day and night is smaller than that of Niigata Prefecture, and is cooler than that of Niigata Prefecture. However, the Aikawa area on the northwestern side of the Ōsado range are affected by the monsoon blowing from the northwest and the temperature is higher. Precipitation on Sado Island is mainly concentrated in the end of the East Asian rainy season and early winter, and there is less precipitation than in Niigata Prefecture. When the low air pressure and typhoons pass through the Sea of Japan, Sado Island often suffers from Foehn wind, raising the temperature sharply. Located at the junction of the warm and cold current, Sado City enjoys diverse plants and rich aquatic resources.
History
With a long history, Sado Island has been inhabited by humans since 10,000 years ago. Thousands of ruins discovered in the Kanai area included stoneware and hunting equipment from the late Yayoi period. There are also records of Sado in the Kojiki and Nihongi. After the Taika Reform, the central government established the Sado Province on the island, and the local population began to emigrate to Sado Island. At the same time, Sado Island has also become the place where losers of political conflicts or dissidents were exiled. Emperor Juntoku, Nichiren and other people had been exiled to Sado. After the Kamakura period, the Honma clan was appointed as the Shugodai. After 1589 ( Tenshō 17), Uesugi Kagekatsu invaded Sado Island, after which Sado Island was dominated by the Uesugi clan.