Seibu Yamaguchi Line

The line traces its origin to an amusement-park attraction. In 1950 Seibu opened the "Otogi Line" (おとぎ線), a single-track 762 mm narrow-gauge light railway whose battery-locomotive-hauled "Fantasy Train" (おとぎ電車 / おとぎ列車) carried sightseers through the recreation area Seibu had developed around the Murayama Reservoir (Lake Tama). The first section, from Tamako Hotel-mae to Kamientei, opened on 1 August 1950, and the following year, on 16 September 1951, the line was extended on to Unesco-mura, with Kamientei downgraded to the Yamaguchi signal post.

On 15 July 1952 the 3.7-kilometre Otogi Line, from Tamako Hotel-mae to Unesco-mura, was reclassified from an amusement ride into a proper local railway under the Local Railway Act and renamed the Yamaguchi Line, giving it the formal name Seibu Yamaguchi Line; the old "Fantasy Train" names nonetheless stayed in popular use. Fares were charged separately from Seibu's other lines, and for many years the railway operated only seasonally, hauled by battery locomotives. Tamako Hotel-mae was renamed Seibu-Yūenchi in 1963 and again to Yūenchi-mae in 1979.

To mark the centenary of railways in Japan, steam-locomotive operation began on 2 June 1972, and from then on steam trains ran on the line outside the winter months, hauling vintage coaches acquired from other light railways. The original German-built Koppel locomotives were borrowed and ageing, so the operation was suspended for track upgrading on 17 December 1976 and resumed on 19 March 1977; once the trackbed had been strengthened and tunnels opened out, even double-headed steam workings became possible.

By the early 1980s the ageing facilities and rolling stock, together with a desire to improve access from the Tamako Line to the Seibu Lions' baseball stadium (today's Belluna Dome), prompted a wholesale rebuilding. The Ministry of Transport authorised the conversion to a new-transit system on 16 April 1984; after a farewell ceremony on 13 May, the "Fantasy Train" made its last run and the line closed for reconstruction on 14 May 1984. Procedurally the old light railway was formally abolished and a fresh AGT licence obtained, and the route was realigned with new terminals.

On 25 April 1985 the line reopened in its present form as a rubber-tyred AGT railway running 2.8 kilometres from Seibu-Yūenchi to Seibukyūjō-mae, and the surviving Yūenchi-mae–Unesco-mura section was abolished the same day; fares were merged into Seibu's ordinary system. The engineers deliberately kept costs down: rather than driverless cab-signal/ATO automation the line was built with conventional lineside signals and ATS for one-person operation, and it adopted 750 V DC electrification with an eye to commercialising VVVF inverter control. The three four-car Series 8500 trainsets built for the opening were Seibu's first VVVF-inverter cars.

The Yamaguchi Line occupies an unusual niche among Japan's automated guideway systems. As of 2019 it was one of only two AGT lines in the country run by a purely private company—the other being the Yamaman Yūkarigaoka Line—and it remains the only guideway line in Japan that crosses a prefectural boundary, threading from Tokyo into Saitama. For most of its length it follows the northern shore of the Lower Murayama Reservoir, though a protective watershed forest screens the lake from view for much of the ride.

More recent changes have refreshed the line without altering its character. On 13 March 2021 its termini were renamed—Seibu-Yūenchi became Tamako and Yūenchi-nishi became Seibuen-yūenchi—and from 1 April 2021 Seibu began running the Leo Liner on electricity from its own solar power station, making it effectively carbon-neutral. On 27 March 2026 the new Series L00, built by Mitsubishi Heavy Industries as the first new trains in some forty years, entered service to replace the Series 8500, with a planned three four-car sets by fiscal 2027.

• 19501 August: Seibu opens the 762 mm narrow-gauge "Otogi Line" light railway, Tamako Hotel-mae–Kamientei, as a battery-locomotive-hauled amusement ride.
• 195116 September: the Otogi Line is extended Kamientei–Unesco-mura; Kamientei is downgraded to the Yamaguchi signal post.
• 195215 July: the 3.7 km Tamako Hotel-mae–Unesco-mura line is reclassified as a local railway under the Local Railway Act and renamed the Yamaguchi Line.
• 19631 July: Tamako Hotel-mae Station is renamed Seibu-Yūenchi.
• 19722 June: steam-locomotive operation begins, marking the centenary of railways in Japan.
• 197617 December: operations are suspended for track-renovation work.
• 197719 March: operations resume after the trackbed is strengthened.
• 197925 March: Seibu-Yūenchi Station is renamed Yūenchi-mae.
• 198416 April: the Ministry of Transport authorises conversion to a new-transit system; the "Fantasy Train" makes its last run and the line closes for reconstruction on 14 May.
• 198525 April: the line reopens as a rubber-tyred AGT railway, Seibu-Yūenchi–Seibukyūjō-mae (2.8 km); the Yūenchi-mae–Unesco-mura section is abolished the same day. Three Series 8500 sets, Seibu's first VVVF-inverter cars, enter service.
• 202113 March: the termini are renamed (Seibu-Yūenchi → Tamako; Yūenchi-nishi → Seibuen-yūenchi); from 1 April the Leo Liner runs on Seibu's own solar power, effectively carbon-neutral.
• 202627 March: the Mitsubishi-built Series L00—the first new trains in some forty years—enters service, replacing the Series 8500.