Kotoden Kotohira Line

The line was built not as a branch of the state railway but by the Kotohira Electric Railway (Kotohira Dentetsu), one of the predecessor companies of today's Kotoden, as one of several rail routes laid toward the Konpira shrine. Before construction its planners toured the big Kansai private railways — Hankyū, Hanshin and Nankai — and resolved to build to a high standard; the line was electrified at 1,500 V from the very start, then an unusually high voltage, with equipment on a par with the leading Kansai operators, and it earned the nickname "the Hankyū of Sanuki." An early plan to follow the Kotohira highway for its whole length was altered, after a lobbying campaign by the Busshōzan district, to route the line through Busshōzan instead.

The first section, between Ritsurin-Kōen and Takinomiya, opened on 21 December 1926. The following year the line was extended at both ends: Takinomiya to Kotohira (the present Kotoden-Kotohira) on 15 March 1927, and Takamatsu — the station now called Kawaramachi — to Ritsurin-Kōen on 22 April 1927, completing the through route across the plain. For its first decades the line terminated at Kawaramachi rather than at the harbour, and as a legacy of that history the zero kilometre post still stands at Kawaramachi Station.

The wartime years reshaped the operator and the station names. The Takamatsu terminus was renamed Kotoden-Takamatsu in August 1941, and the Kotohira terminus became Kotoden-Kotohira in 1942. Then on 1 November 1943 three local companies — the Sanuki Electric Railway, the Kotohira Electric Railway and the Takamatsu Electric Tramway — merged to form the Takamatsu-Kotohira Electric Railroad, bringing the Kotohira Line under the Kotoden name it still carries.

After the war Kotoden extended the line the last short distance to the waterfront as the Chikkō Line. The Kataharamachi–Kotoden-Takamatsu section opened on 18 February 1948 and the Chikkō (a temporary station)–Kataharamachi section on 26 December 1948; the new stretch was double-tracked on 11 May 1949. In a complex 1953 rearrangement the Chikkō section was converted from double track to single-track parallel working, with the former down line stepped down to 600 V so that the Shido Line could run into it. On 1 January 1954 the Chikkō terminus was renamed Takamatsu-Chikkō and Kotoden-Takamatsu became Kawaramachi, and on 10 September 1955 the present Takamatsu-Chikkō Station opened and the temporary station closed.

Through the late 1950s and 1960s the line carried heavy pilgrim traffic to Konpira. Sanjō Station opened on 1 March 1956, and on 1 March 1958 a Sue signal box was added and an express service — the "Konpira" — began, calling only at Kawaramachi and Ritsurin-Kōen between Takamatsu and the shrine. As pilgrims increasingly switched to sightseeing buses and private cars, the express was discontinued on 1 April 1967 and the line settled into a chiefly local-transport role. The Chikkō section's former down line was raised back to 1,500 V on 2 August 1966, and on 21 May 1967 that section was converted from single-track parallel working back to conventional double track. Automatic train stop (ATS) was installed on 17 February 1978.

In the 21st century the line has gained new suburban stations on the Takamatsu side and has begun a long programme of partial double-tracking. Kūkō-dōri Station opened on 29 July 2006, Ayagawa Station — beside an Aeon mall — on 15 December 2013, and Fuseishi Station on 28 November 2020; the Sanjō–Ōta section was double-tracked on 1 November 2020, just before Fuseishi opened, and the Ritsurin-Kōen–Sanjō section followed on 20 March 2026.

Today the Kotoden Kotohira Line is the busiest of the three Kotoden routes, running standard-gauge electric multiple units — many of them former Kansai- and Tokyo-area commuter cars — at frequent intervals on the Takamatsu side and less often out toward Kotohira. Double track now reaches inland from Takamatsu-Chikkō, while most of the line beyond remains single track, and it continues to link central Takamatsu with the Konpira shrine and the towns of the Sanuki Plain. At Kotoden-Kotohira it meets JR Shikoku's Dosan Line at Kotohira Station, the one state-railway route to Kotohira that has outlasted the several private and tramway lines that once converged on the shrine town.

• 192621 December: the Kotohira Electric Railway opens the first section, Ritsurin-Kōen–Takinomiya, electrified at 1,500 V DC.
• 192715 March: Takinomiya–Kotohira (now Kotoden-Kotohira) opens; 22 April: Takamatsu (now Kawaramachi)–Ritsurin-Kōen opens, completing the through route.
• 1941August: the Takamatsu terminus is renamed Kotoden-Takamatsu. (The connecting Shionoe Line at Busshōzan had closed on 10 May 1941.)
• 1942The Kotohira terminus is renamed Kotoden-Kotohira.
• 19431 November: the Sanuki Electric Railway, the Kotohira Electric Railway and the Takamatsu Electric Tramway merge to form the Takamatsu-Kotohira Electric Railroad (Kotoden).
• 194818 February: the Chikkō Line section Kataharamachi–Kotoden-Takamatsu opens; 26 December: Chikkō (a temporary station)–Kataharamachi opens.
• 194911 May: the Chikkō Line (Chikkō–Kotoden-Takamatsu) is double-tracked.
• 195320 October: the Chikkō Line is changed from double track to single-track parallel working; the former down line is stepped down to 600 V and the Shido Line begins running into it.
• 19541 January: Chikkō Station is renamed Takamatsu-Chikkō and Kotoden-Takamatsu Station is renamed Kawaramachi.
• 195510 September: the present Takamatsu-Chikkō Station opens and the temporary station is closed.
• 19561 March: Sanjō Station opens.
• 19581 March: a Sue signal box opens and the 'Konpira' express service begins, calling only at Kawaramachi and Ritsurin-Kōen between Takamatsu and Kotohira.
• 19662 August: the Chikkō Line's former down line is raised back to 1,500 V.
• 19671 April: the 'Konpira' express is discontinued; 21 May: the Chikkō Line is converted from single-track parallel working back to double track.
• 197817 February: automatic train stop (ATS) is installed.
• 200629 July: Kūkō-dōri Station opens.
• 201315 December: Ayagawa Station (beside an Aeon mall) opens.
• 20201 November: the Sanjō–Ōta section is double-tracked; 28 November: Fuseishi Station opens.
• 202620 March: the Ritsurin-Kōen–Sanjō section is double-tracked.