# Kōsa, Kumamoto

Kōsa (甲佐町, Kōsa-machi) is a town located in Kamimashiki District, Kumamoto Prefecture, Japan. As of 31 July 2024, the town had an estimated population of 10,004 in 4,441 households, and a population density of 24 persons per km$^2$. The total area of the town is 57.93 km$^2$ (22.37 sq mi).

## Geography

Kōsa is located in the central inland region of Kumamoto Prefecture, about 20 kilometers southeast of Kumamoto City. The northwestern part is at the southeastern edge of the Kumamoto Plain, but most of the town area is included in the Kyushu Mountains and is at a high altitude. The Midorigawa River, a first-class river, flows through the center of the town.

### Neighboring municipalities

Kumamoto Prefecture
* Kumamoto
* Mifune
* Misato
* Uki

### Climate

Kōsa has a humid subtropical climate (Köppen climate classification Cfa) with hot, humid summers and cool winters. There is significant precipitation throughout the year, especially during June and July. The average annual temperature in Kōsa is 16.3 °C (61.3 °F). The average annual rainfall is 2,145.6 mm (84.47 in) with June as the wettest month. The temperatures are highest on average in August, at around 27.1 °C (80.8 °F), and lowest in January, at around 5.4 °C (41.7 °F). The highest temperature ever recorded in Kōsa was 37.9 °C (100.2 °F) on 14 August 2018; the coldest temperature ever recorded was −8.8 °C (16.2 °F) on 25 January 2016.
Climate data for Kōsa (1991−2020 normals, extremes 1977−present) :
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Record high °C (°F) | 22.0 (71.6) | 25.1 (77.2) | 28.8 (83.8) | 30.0 (86.0) | 34.0 (93.2) | 35.7 (96.3) | 37.9 (100.2) | 37.9 (100.2) | 36.2 (97.2) | 32.9 (91.2) | 27.9 (82.2) | 24.6 (76.3) | 37.9 (100.2) |
| Mean daily maximum °C (°F) | 10.6 (51.1) | 12.3 (54.1) | 15.9 (60.6) | 21.3 (70.3) | 26.0 (78.8) | 28.0 (82.4) | 31.6 (88.9) | 33.0 (91.4) | 29.7 (85.5) | 24.7 (76.5) | 18.6 (65.5) | 12.8 (55.0) | 22.0 (71.7) |
| Daily mean °C (°F) | 5.4 (41.7) | 6.7 (44.1) | 10.1 (50.2) | 15.0 (59.0) | 19.5 (67.1) | 23.0 (73.4) | 26.5 (79.7) | 27.1 (80.8) | 23.8 (74.8) | 18.5 (65.3) | 12.8 (55.0) | 7.4 (45.3) | 16.3 (61.4) |
| Mean daily minimum °C (°F) | 0.9 (33.6) | 1.7 (35.1) | 4.7 (40.5) | 9.2 (48.6) | 14.1 (57.4) | 18.9 (66.0) | 22.6 (72.7) | 22.9 (73.2) | 19.5 (67.1) | 13.5 (56.3) | 8.0 (46.4) | 2.8 (37.0) | 11.6 (52.8) |
| Record low °C (°F) | −8.8 (16.2) | −7.2 (19.0) | −3.5 (25.7) | −0.8 (30.6) | 5.7 (42.3) | 9.6 (49.3) | 16.5 (61.7) | 15.1 (59.2) | 8.0 (46.4) | 2.4 (36.3) | −2.7 (27.1) | −4.8 (23.4) | −8.8 (16.2) |
| Average precipitation mm (inches) | 71.5 (2.81) | 97.3 (3.83) | 133.9 (5.27) | 141.1 (5.56) | 169.1 (6.66) | 473.7 (18.65) | 395.2 (15.56) | 190.0 (7.48) | 201.7 (7.94) | 103.0 (4.06) | 94.7 (3.73) | 74.6 (2.94) | 2,145.6 (84.47) |
| Average precipitation days (≥ 1.0 mm) | 8.2 | 9.2 | 11.6 | 10.5 | 10.1 | 15.5 | 13.5 | 11.4 | 10.3 | 7.7 | 8.3 | 8.6 | 124.9 |
| Mean monthly sunshine hours | 118.5 | 130.5 | 155.8 | 174.6 | 182.4 | 119.9 | 169.3 | 195.8 | 161.5 | 167.4 | 138.4 | 124.4 | 1,844.7 |
| Source: Japan Meteorological Agency ||||||||||||||

### Demographics

Per Japanese census data, the population of Kōsa in 2020 is 10,132 people. Kōsa has been conducting censuses since 1920.
| Year | Pop. | ±% |
| 1920 | 13,880 | — |
| 1925 | 14,629 | +5.4% |
| 1930 | 15,457 | +5.7% |
| 1935 | 15,630 | +1.1% |
| 1940 | 15,314 | −2.0% |
| 1945 | 19,517 | +27.4% |
| 1950 | 19,915 | +2.0% |
| 1955 | 18,610 | −6.6% |
| 1960 | 16,765 | −9.9% |
| 1965 | 14,975 | −10.7% |
| 1970 | 13,620 | −9.0% |
| Year | Pop. | ±% |
| 1975 | 13,160 | −3.4% |
| 1980 | 12,989 | −1.3% |
| 1985 | 12,864 | −1.0% |
| 1990 | 12,459 | −3.1% |
| 1995 | 12,372 | −0.7% |
| 2000 | 12,012 | −2.9% |
| 2005 | 11,604 | −3.4% |
| 2010 | 11,180 | −3.7% |
| 2015 | 10,717 | −4.1% |
| 2020 | 10,132 | −5.5% |
Kōsa population statistics :

## History

The area of Kōsa was part of ancient Higo Province, During the Edo Period it was part of the holdings of Kumamoto Domain. After the Meiji restoration, the town of Kōsa and villages of Miyauchi, Tatsuno, Shirahata, and Otome were established with the creation of the modern municipalities system on April 1, 1889. On January 1, 1955 Miyauchi, Tatsuno, Shirahata, and Otome merged with Kōsa.

## Government

Kōsa has a mayor-council form of government with a directly elected mayor and a unicameral town council of 11 members. Kōsa, collectively with the other municipalities of Kamimashiki District contributes two members to the Kumamoto Prefectural Assembly. In terms of national politics, the town is part of the Kumamoto 3rd district of the lower house of the Diet of Japan.

## Economy

The local economy relies on agriculture, and Kōsa's geographic position as a logistics hub.

## Education

Kōsa has four public elementary schools and one public junior high school operated by the town government, and one public high schools operated by the Kumamoto Prefectural Board of Education.

## Transportation
### Railways

Kōsa does not have any passenger railway service. The nearest station is Matsubase Station on the JR Kyushu station is Matsubase Station on the Kagoshima Main Line in neighboring Uki.

### Highways

* Kyushu Expressway
* National Route 443

## Sports

Since its inception in 1983, the Kumamoto Kōsa 10-Miler road race has seen several top rated achievements being set during the event, which is run in December. The most recent new world record for the 10 miles was set in December 2022 by Bernard Koech.