The is a rapid transit system in Osaka, Japan, operated by Osaka Metro. The line runs east-westerly under . Its official name is , and in MLIT publications, it is written as . Station numbers are indicated by the letter C. Together with the through operation to the Keihanna Line, the two lines have a unified nickname . On 1 July 2005, Osaka City bought the from Cosmosquare to Osakakō of its subsidiary , reducing fare to increase traffic. The section became a part of the Chūō Line, however is still owned by OTS. The Chūō Line is the only line to connect to all other railway lines operated by the Osaka Municipal Transportation Bureau, including the Nankō Port Town Line. History The line (initially known as Line No. 4) opened on December 11, 1961, initially running between Ōsakakō and Bentenchō (this was the first elevated portion of the Osaka subway system); trains were initially composed of one car. Between 1964 and 1985, the line was expanded towards Nagata in four stages: 31 October 1964: Section between Bentenchō and Hommachi opens, with intermediate stations at Kujo and Awaza. 30 September 1967: The section between Tanimachi 4-chome and Morinomiya opens as a shuttle service with 2-car trains. 29 July 1968: The section of the shuttle service between Morinomiya and Fukaebashi opens. 6 December 1969: The section between Hommachi and Tanimachi 4-chome (including Sakaisuji-Hommachi) opens after construction delays; the shuttle service between Tanimachi 4-chome and Fukaebashi was absorbed into the line, which was now named the Chūō Line. 4-car trains begin operation. 5 April 1985: The section between Fukaebashi and Nagata opens. 6-car trains begin operation. 1 October 1986: Through service to Ikoma commences upon the opening of the Kintetsu Keihanna Line (then named the Higashiosaka Line). On 18 December 1997, the OTS Technoport Line opened between Ōsakakō and Cosmosquare. This line was absorbed into the Chūō Line on 1 July 2005. The Keihanna Line was extended further into Nara when the extension to Gakken Nara-Tomigaoka opened on 27 March 2006. Future Plans The North Technoport Line is a planned extension of the Chūō line from Cosmosquare to Yumeshima, Maishima, and Sakurajima. The section to Yumeshima is currently under construction with a projected completion date of 2024, in advance of the Osaka 2025 Expo. Separately, a new station is planned to be built on the spur track to the Morinomiya depot facility