Tenryū Hamanako Line

The route originated in a plan, added to the appendix of the amended Railway Construction Act as the "Enbi Line," to run from Kakegawa via Tōtōmi-Futamata and Mikawa-Ōno to Ōi (present-day Ena) in the Tōnō region of Gifu Prefecture. For military reasons, however, the section between Tōtōmi-Futamata and Shinjohara was added to the appendix as item No. 63-2 in 1933 and built as a strategic bypass: the Tōkaidō Main Line ran close to the coast near Lake Hamana and was thought vulnerable to enemy attack and to disruption of its lake bridge, so an inland alternative away from the shoreline was wanted. Near Tenryū-Futamata, construction reused part of the abandoned trackbed of the Kōmei Electric Railway, which had existed from 1929 to 1935.

Construction proceeded from both ends. The Futamata Line opened first, between Kakegawa and Enshū-Mori (then Tōtōmi-Mori), a distance of 12.9 km, on 17 April 1935. Work then advanced from the western end: on 1 December 1936 the Futamata-Nishi (West) Line opened between Shinjohara and Mikkabi, 12.1 km, and the original Futamata Line was renamed the Futamata-Higashi (East) Line. The western line was extended from Mikkabi to Kanasashi, 13.8 km, on 1 April 1938. The two construction fronts were joined on 1 June 1940 when the Enshū-Mori–Kanasashi section, 29.1 km, opened, completing the through route between Kakegawa and Shinjohara; the eastern line absorbed the new section and the western line and the whole route was renamed the Futamata Line.

As intended, the line served as a wartime detour for the Tōkaidō Main Line on several occasions. When the trunk line was badly damaged by the Tōnankai earthquake in December 1944, trains were diverted over the Futamata Line until repairs were complete. It was used again in July 1945, when the Tōkaidō Main Line was severed by air raids on 24 July and when the Hamamatsu area was put out of action by naval bombardment accompanying the Hamamatsu air raid on 30 July, military and main-line trains being rerouted over the line on both occasions.

In the post-war decades the line was modernised and new stations were added along its length. Steam locomotives were withdrawn and the line fully dieselised on 31 March 1971. Under JNR's programme to shed loss-making rural railways, the Futamata Line was designated a Specified Local Line and approved for conversion in the second round of such designations on 22 June 1984; scheduled freight services were discontinued on 14 March 1985.

On 15 March 1987, the 67.9-km JNR Futamata Line was formally abolished and reopened the same day as the 67.7-km Tenryū Hamanako Line under the new third-sector operator Tenryū Hamanako Railroad — only weeks before Japanese National Railways was itself privatised on 1 April 1987. On takeover, two new stations were opened and several stations were renamed, including Tōtōmi-Futamata to Tenryū-Futamata. The new company continued to open additional stations over the following decades, and a large number of the line's pre-war structures — bridges, tunnels and station buildings — have since been registered as Registered Tangible Cultural Properties of Japan, with 5 listed in 1998 and a further 31 in 2011; the English article gives a total of thirty-six such features.

• 1933The Tōtōmi-Futamata–Shinjohara section is added to the appendix of the amended Railway Construction Act (item No. 63-2) so it can be built as a strategic bypass of the coastal Tōkaidō Main Line.
• 193517 April: the Futamata Line opens between Kakegawa and Enshū-Mori (then Tōtōmi-Mori), 12.9 km.
• 19361 December: the Futamata-Nishi (West) Line opens between Shinjohara and Mikkabi, 12.1 km; the original line is renamed the Futamata-Higashi (East) Line.
• 19381 April: the Futamata-Nishi Line is extended from Mikkabi to Kanasashi, 13.8 km.
• 19401 June: the Enshū-Mori–Kanasashi section, 29.1 km, opens, completing the through route between Kakegawa and Shinjohara; the eastern and western lines are merged and renamed the Futamata Line.
• 1944December: the Futamata Line serves as a detour for the Tōkaidō Main Line after that line is damaged by the Tōnankai earthquake.
• 1945July: the line is again used as a wartime detour — for three trains when the Tōkaidō Main Line is severed by air raids on 24 July, and for military and main-line trains when the Hamamatsu area is hit by naval bombardment on 30 July.
• 197131 March: steam locomotives are withdrawn and the line is fully dieselised.
• 198422 June: the Futamata Line is approved for conversion as a Specified Local Line in the second round of such designations.
• 198514 March: scheduled freight services on the line are discontinued.
• 198715 March: the 67.9-km JNR Futamata Line is abolished and reopens the same day as the 67.7-km Tenryū Hamanako Line under the third-sector Tenryū Hamanako Railroad; two new stations open and several are renamed (e.g. Tōtōmi-Futamata to Tenryū-Futamata). JNR is privatised weeks later, on 1 April 1987.
• 198813 March: the Kakegawa–Kanasashi section is switched to electronic block working and five new stations open — Ikoinohiroba, Harada, Enden, Hamamatsu-Daigaku-mae (now Tokohadaigakumae) and Okuhamanako.
• 199618 March: Kakegawa-shiyakusho-mae and Fruit Park stations open.
• 201514 March: Morimachibyōin-mae Station opens; Kigakōkō-mae Station is renamed Okaji.
• 201627 August: the line signs a sister-railway agreement with the Jiji Line of the Taiwan Railways Administration.