Takamori Line

The line began as a state project. On 12 February 1928 the Japanese Government Railways opened the Tateno–Takamori section as the Miyaji Line (宮地線). Later the same year, on 2 December 1928, when the Hōhi Main Line was completed through Aso, the branch to Takamori was separated from it and renamed the Takamori Line.

As a lightly used rural line, it was caught up in the rationalisation of the national railways. On 1 September 1981 it was designated a First-Category Specified Local Transportation Line, marking it for discontinuation as a Japanese National Railways operation. Freight services ended on 1 February 1984, and on 17 November of that year the decision was taken to convert the line to third-sector operation rather than close it outright.

The Minamiaso Railway took over the Takamori Line from Japanese National Railways on 1 April 1986, on the eve of JNR's nationwide breakup. The new operator quickly added stations to serve local communities: Kase and Miharashidai opened on 1 November 1986. Further infill stations followed over the next decades — including, on 1 April 1992, a station whose full name, Minami-Aso-mizu-no-umareru-sato-Hakusui-kōgen, was then the longest station name in Japan — with Minami-Aso-Shirakawa-Suigen added on 17 March 2012.

The line was thrown into crisis by the Kumamoto earthquakes of April 2016. Services across the whole line were suspended from 14 April 2016, and when the main shock struck on 16 April it caused severe damage on the Tateno–Chōyō section at the western end, where tunnels and bridges — among them the First Shirakawa Bridge and the Saikakuyama and Toshimo tunnels — were cracked and deformed. The eastern part of the line was restored first: the Nakamatsu–Takamori section reopened on 31 July 2016, while the damaged western section remained closed for years of reconstruction.

Rebuilding the Tateno–Chōyō section was a major undertaking, supported by public funding because the small operator could not bear the cost alone. As part of the recovery framework, the line shifted to a vertical-separation model on 1 April 2023: a newly established body, the South Aso Railway Management Organization, became the Type III operator owning and maintaining the infrastructure, while the Minamiaso Railway continued as the Type II operator running the trains.

Full service was finally restored on 15 July 2023, when the Tateno–Nakamatsu section reopened and trains ran the length of the line for the first time since the earthquakes. The reopening also introduced through-running onto the JR Kyushu network: two morning round-trips began operating beyond Tateno over the Hōhi Main Line to Higo-Ōzu Station, giving the Aso caldera a direct rail link toward Kumamoto. On the same day Aso-Shimoda-jō-Fureai-Onsen Station was renamed Aso-Shimoda-jō.

• 192812 February: the Japanese Government Railways opens the Tateno–Takamori section as the Miyaji Line.
• 19282 December: on completion of the Hōhi Main Line, the branch is separated and renamed the Takamori Line.
• 19811 September: the line is designated a First-Category Specified Local Transportation Line, marking it for discontinuation.
• 19841 February: freight services end on the line.
• 198417 November: the decision is taken to convert the line to third-sector operation rather than close it.
• 19861 April: the Minamiaso Railway takes over the Takamori Line from Japanese National Railways.
• 19861 November: Kase and Miharashidai stations open.
• 19921 April: Minami-Aso-mizu-no-umareru-sato-Hakusui-kōgen Station opens, then the longest station name in Japan.
• 201217 March: Minami-Aso-Shirakawa-Suigen Station opens.
• 201614 April: services are suspended across the whole line owing to the Kumamoto earthquakes.
• 201616 April: the main shock severely damages the Tateno–Chōyō section, cracking and deforming tunnels and bridges including the First Shirakawa Bridge.
• 201631 July: the Nakamatsu–Takamori section reopens, while the western section stays closed for reconstruction.
• 20231 April: the line shifts to vertical separation — the South Aso Railway Management Organization becomes the Type III infrastructure operator and the Minamiaso Railway the Type II operator running the trains.
• 202315 July: the Tateno–Nakamatsu section reopens, restoring full-line service for the first time since 2016; two morning round-trips begin through-running over the Hōhi Main Line to Higo-Ōzu, and Aso-Shimoda-jō-Fureai-Onsen Station is renamed Aso-Shimoda-jō.