Jump to content

Kosai, Shizuoka

Coordinates: 34°43′6.4″N 137°31′53.8″E / 34.718444°N 137.531611°E / 34.718444; 137.531611
From Wikipedia, the free encyclopedia
Kosai City Hall
Kosai City Hall
Flag of Kosai
Official seal of Kosai
Location of Kosai in Shizuoka Prefecture
Location of Kosai in Shizuoka Prefecture
Kosai is located in Japan
Coordinates: 34°43′6.4″N 137°31′53.8″E / 34.718444°N 137.531611°E / 34.718444; 137.531611
RegionChūbu (Tōkai)
 • - MayorTakeshi Kageyama [1]
 • Total86.56 km2 (33.42 sq mi)
 (October 2020)
 • Total57,885
 • Density670/km2 (1,700/sq mi)
Time zoneUTC+9 (Japan Standard Time)
- TreeJapanese black pine
- FlowerCommon Gardenia
Phone number053-576-1111
Address3268 Kibi, Kosai-shi, Shizuoka-ken 431-0492
WebsiteOfficial website

Kosai (湖西市, Kosai-shi) is a city located in far western Shizuoka Prefecture, Japan. As of 30 June 2019, the city had an estimated population of 57,885 in 24,232 households,[2] and a population density of 668.7 persons per km2. The total area of the city is 85.65 square kilometres (33.07 sq mi).


Kosai is located in the far southwest corner of Shizuoka Prefecture, bordered by Aichi Prefecture to the west, Lake Hamana to the east. The name of the city means "west of the lake", in reference to its location near Lake Hamana. The city is bordered to the south by the Enshū Gulf of Pacific Ocean. Due to its location, the warm Kuroshio Current offshore provides for a temperate maritime climate with hot, humid summers and mild, cool winters.

Neighboring municipalities[edit]

Shizuoka Prefecture

Aichi Prefecture


Per Japanese census data,[3] the population of Kosau has been relatively steady over the past 30 years.

Historical population
1940 30,843—    
1950 38,884+26.1%
1960 41,449+6.6%
1970 46,126+11.3%
1980 54,252+17.6%
1990 59,926+10.5%
2000 60,827+1.5%
2010 60,043−1.3%
2020 57,885−3.6%


The city has a climate characterized by characterized by hot and humid summers, and relatively mild winters (Köppen climate classification Cfa). The average annual temperature in Kosai is 16.0 °C. The average annual rainfall is 1942 mm with September as the wettest month. The temperatures are highest on average in August, at around 27.3 °C, and lowest in January, at around 5.5 °C.[4]


The area around Kosai has been noted for the production of Japanese pottery and porcelain since the Kofun period. During the Edo period, Kosai was tenryō territory administered directly by the Tokugawa shogunate, and the location of a barrier gate regulating traffic on the old Tōkaidō highway connecting Edo with Kyoto. A post station named Shirasuka-juku developed near the barrier, and this was the forerunner of modern Kosai. During the establishment of the modern municipalities system of the early Meiji period in 1889, the area was reorganized into five villages within Hamana District, Shizuoka. Four of these villages (Washizu, Iride, Shirasuka, Chibata) merged to form the city of Kosai on January 1, 1972.

On March 23, 2010, the town of Arai (from Hamana District) was merged into Kosai. Hamana District was dissolved as a result of this merger.[5]


Kosai has a mayor-council form of government with a directly elected mayor and a unicameral city legislature of 18 members. The city contributes one member to the Shizuoka Prefectural Assembly.


The economy of Kosai is dominated by light manufacturing of automobile components and electronics, as well as commercial fishing. Kosai is home to Suzuki Motor Corporation's Kosai Assembly Plant, Suzuki's main domestic production plant as well as to plants owned by Panasonic and Sony. Commercial fishing and aquaculture on Lake Hamana is also a component of the city's economy.


Kosai has six public elementary schools and five public middle schools operated by the city government. The city has two public high schools operated by the Shizuoka Prefectural Board of Education. The prefecture also operates a special education school for the handicapped.

The ENE - Escola Nova Era, a Brazilian international school[6] is also located in Kosai. During 1971-1992 a Swedish school was located in Chibata.




Sister city relations[edit]

Local attractions[edit]

Notable people from Kosai[edit]


  1. ^ "Kosai official website mayor's page". www.city.kosai.shizuoka.jp (in Japanese). Retrieved 2022-03-21.
  2. ^ Kosai City official statistics (in Japanese)
  3. ^ Kosai population statistics
  4. ^ Kosai climate data
  5. ^ "市町村合併情報 静岡県 <国土地理協会>". Archived from the original on 2007-07-28. Retrieved 2008-09-08.
  6. ^ "Escolas Brasileiras Homologadas no Japão " (Archive). Embassy of Brazil in Tokyo. Retrieved on October 13, 2015.
  7. ^ "International Exchange". List of Affiliation Partners within Prefectures. Council of Local Authorities for International Relations (CLAIR). Archived from the original on 13 January 2016. Retrieved 21 November 2015.

External links[edit]

Media related to Kosai, Shizuoka at Wikimedia Commons