The Koumi Line (小海線, Koumi-sen) is a railway line in Japan operated by East Japan Railway Company (JR East). It links Kobuchizawa Station in Hokuto, Yamanashi with Komoro Station in Komoro, Nagano, and extends 78.9 km (49.0 mi) through the mountains with a total of 31 stations. It roughly follows the route of National Route 141, paralleling the road at some places and crossing it twice.

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Quick Facts Overview, Native name ...

Koumi Line
JR East KiHa 110 series DMU on the Koumi Line
Overview
Native name	小海線
Status	In operation
Owner	JR East
Locale	Yamanashi, Nagano prefectures
Termini	Kobuchizawa Komoro
Stations	31
Service
Type	Regional rail
Operator(s)	JR East
Rolling stock	KiHa E200 DMU, KiHa 110 series DMU
History
Opened	1919
Technical
Line length	78.9 km (49.0 mi)
Number of tracks	Entire line single tracked
Character	Rural and scenic
Track gauge	1,067 mm (3 ft 6 in)
Electrification	None
Operating speed	85 km/h (53 mph)
Route map

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All local trains stop at all stations. Extra rapid trains stop at specific stations.

Some of the stations along the Koumi Line are among the highest in Japan, with Nobeyama Station reaching 1,345 meters (4,413 ft) above sea level. Because of the frequent stops and winding route, the full 78.9 kilometers (49.0 mi) journey often takes as long as two and a half hours to traverse. However, the journey is known for its scenery, in which passengers can see nature, highlands, high mountains and one of the most beautiful starlit skies at night.^[1][2][3]

Local trains run between Koumi or Nakagomi and Komoro, between Kobuchizawa and Nobeyama or Koumi respectively, excluding local trains running the full length of the line. In 2022, JR East announced the names of railway lines which were failing to make a profit, which included the section of this line between Koumi and Kobuchizawa.^[4][5]

Local trains are driver-only operated (one-person operation) between Nakagomi and Kobuchizawa. However, lots of passengers use the stations between Nakagomi and Komoro, so local trains in this section have conductors onboard.

Nakagomi Station is located near the Koumi Line Operation Office, where many train staff are working.

Legend

◇・∨・∧ - passing loop

｜ - no passing loop

• KiHa 110 series DMUs, since November 1991
• KiHa E200 hybrid DMUs, since July 2007

• A two-car KiHa 110 series train on the Koumi Line, April 2008
• A two-car KiHa E200 series train on the Koumi Line, April 2009

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The Saku Railway opened the section from Komoro to Haguroshita in 1915, and extended the line to Koumi in 1919. The company planned a railway network extending from Kōfu in the south to Naoetsu and Nagaoka in the north, linking up with the Fuji Minobe Railway to create a coast-to-coast rail line. North of Komoro, Saku Railway obtained a construction permit for a section between Yashiro and Suzaka, but this was transferred to the local Katō Railway (predecessor of the Nagano Electric Railway). Due to World War I construction of the line south of Koumi was not undertaken. Diesel railcars were introduced on the line in 1930.

The Koumi - Saku-Uminokuchi section was opened in 1932 by Japanese National Railways (JNR), which also opened the Kobuchizawa — Kiyosato section in 1933. The Saku Railway was nationalised in 1934, and the Saku-Uminokuchi - Kiyosato section opened in 1935, completing the line.

In July 2017, JR East launched the tourist train High Rail 1375. "1375" refers to the elevation of 1,375 m of the highest point on any JR line in Japan. The train makes the most of its backdrop, and offers unique services for day and night operations.^[7]

• List of railway lines in Japan