The Oga Peninsula, lying slightly north of the City of Akita, protrudes very distinctly into the Japan Sea. The Oga-sen follows the Bay on the south side of the Oga Peninsula as far as the community of Oga.
Trains start at the Akita terminal and run up the Ô'u Honsen to a point slightly beyond the station of Oiwake (13 km from Akita). There they branch off to the west onto the Oga-sen (26, 6 km from Oiwake). First they pass through small, mostly rural settlements and then cross the channel linking the sea to the Hachirôgata Chôseichi (Hachirôgata Retention Basin). Hachirôgata once was a large lake on the east side of the mountains which form the tip of Oga Peninsula; most of Hachirôgata was turned into a huge rice-farming flatland by 1964, leaving only a small stretch of fresh water in the area. The border between the fresh and the Japan Sea's salt water is today guarded by a barrage, which can be seen to the north of the railway bridge. After Wakimoto halt (18, 9 km from Oiwake) trains climb through wilder countryside and over a small pass down into the port area and the little town of Oga. Until 2002 the line continued (freight only) for 1, 8 km to the port of Funagawa Minato.
The Oga-sen has been diesel worked in the past, but in March 2017 an experimental battery electric train (EV E-800/801) came into service. This train is JR East Japan's first battery train for 20 kV / 50 Hz AC, and batteries are recharged at the Oga terminal via the pantograph. Between Akita and Oiwake current is taken from the overhead catenary, the pantograph being lowered (or raised) during the stop at Oiwake. The full replacement of the diesel trains by battery electric trains is expected shortly.
The line to Oga began as a light railway in 1913, in 1922 becoming the Funagawa-sen. In 1937 the continuation to the port was opened; in 1968 the line was renamed "Oga-sen". Until 2001 freight trains were worked carrying oil from the regional oil fields. In 2019 the Oga-sen was worked basically by 15 stopping trains daily.
