Kibi Line

The line was not built by the state. Together with the neighbouring Tsuyama Line, it was opened by the Chūgoku Railway, a private company that survives today as the bus operator Chūtetsu Bus. The Kibi Line's first section, branded the Chūgoku Railway Kibi Line, opened on 15 November 1904 between Okayama and Tatai (13.5 miles, about 21.73 km), with intermediate stations at Mikado (now Bizen-Mikado), Ichinomiya (now Bizen-Ichinomiya), Kibitsu, Inari (now Bitchū-Takamatsu), Ashimori and Sōja (now Higashi-Sōja). Although the surrounding Kibi-ji is now valued chiefly as a tourist district, the line was originally built to connect Okayama with the river traffic of the Takahashi River, and it therefore skirted the north of the Sōja town centre and terminated at Tatai, a transfer point with boats serving Takahashi and Niimi.

The railway was extended and reshaped over its first decades. Hattori Station opened in 1908, and in 1911 the company opened the short Inariyama Line, a 1.5-mile (about 2.41 km) branch from Inari to Inariyama that connected on foot with the Chūgoku Inariyama cable railway. Anticipating that the new Hakubi Line (then the Hakubi South Line) would cause the river traffic to decline, the Chūgoku Railway abolished the line on to Tatai on 17 February 1925 and, on 7 August 1925, opened a short extension from Sōja to Nishi-Sōja, running into the government railway's station there.

As in the rest of Japan, the private company was caught up in the wartime nationalisation of railways. On 1 June 1944 the railway division of the Chūgoku Railway was nationalised and became the Kibi Line of Japanese National Railways (JNR), while the company itself lived on as the bus operator Chūtetsu Bus. At nationalisation the dormant Inariyama Line was abolished and the main line's length adjusted slightly, and Mikado Station was renamed Bizen-Mikado. In 1959 the original Sōja Station was renamed Higashi-Sōja and the former Nishi-Sōja took the name Sōja, giving the line its present western terminus.

Under JNR the line was modernised and its goods role wound down. Centralised traffic control was introduced on 30 September 1968, freight handling on the line ceased in 1970, and steam locomotives were retired on 25 March 1971; passenger trains, which had earlier run through onto the Tsuyama and Inbi lines as far as Tottori, were progressively standardised on diesel railcars. With the privatisation and break-up of JNR on 1 April 1987, the Kibi Line passed to the newly formed West Japan Railway Company (JR West), under which one-man operation was later introduced and the line came to be managed from JR West's regional organisation in the Chūgoku region.

In the modern era the line has acquired its tourist identity and become the subject of light-rail proposals. From the timetable revision of 26 March 2016 JR West assigned it the line symbol "U" and a pink line colour and began promoting it as the "Momotarō Line," linking it to the Momotarō folk tale rooted in the old Kibi country. A conversion of the line to light rail (LRT) has been discussed since 2003, when JR West announced it was studying turning the Kibi Line into a tramway; by 2014 a three-party planning committee of Okayama City, Sōja City and JR West had been formed, and in April 2018 the three parties formally agreed to convert the line to LRT, aiming to begin operation roughly ten years later. The COVID-19 pandemic intervened: on 7 February 2021 the three-party talks were reported to be heading for suspension, as the railway's sharp drop in revenue and the cities' worsening finances made the looming rise in project spending hard to bear, and the 2018 timetable was expected to slip substantially.

• 190415 November: the Chūgoku Railway Kibi Line opens between Okayama and Tatai (13.5 miles, ~21.73 km), with stations at Mikado, Ichinomiya, Kibitsu, Inari, Ashimori and Sōja (now Higashi-Sōja).
• 190820 April: Hattori Station opens.
• 19111 May: the Chūgoku Railway opens the Inariyama Line, a 1.5-mile (~2.41 km) branch from Inari to Inariyama.
• 192517 February: the Sōja–Tatai section is abolished and Tatai Station closes; on 7 August a Sōja–Nishi-Sōja extension opens, running into the government railway's Nishi-Sōja Station.
• 19319 February: Inari Station is renamed Bitchū-Takamatsu.
• 19441 June: the railway division of the Chūgoku Railway is nationalised and becomes the JNR Kibi Line; the dormant Inariyama Line is abolished and Mikado Station is renamed Bizen-Mikado (the company survives as the bus operator Chūtetsu Bus).
• 19591 October: the original Sōja Station is renamed Higashi-Sōja; on 1 November the former Nishi-Sōja Station is renamed Sōja, becoming the present western terminus.
• 196830 September: centralised traffic control (CTC) is introduced on the line.
• 197125 March: steam-locomotive operation ends and the line is fully dieselised.
• 19871 April: with the privatisation and break-up of JNR, the Kibi Line passes to the West Japan Railway Company (JR West).
• 201626 March: from this timetable revision the line is given the line symbol 'U' and a pink line colour and branded the 'Momotarō Line'.
• 2018April: Okayama City, Sōja City and JR West formally agree to convert the line to light rail (LRT), aiming to begin operation roughly ten years later; the three-party talks were later reported on 7 February 2021 to be heading for suspension amid COVID-19 finances.