Tobu Daishi Line

The line is a surviving fragment of a far more ambitious scheme known as the Nishi-Ita Line (西板線). After Tobu Railway absorbed the Tōjō Railway in 1920, the company planned an 11.6-kilometre connection from Nishiarai on the Isesaki Line to Kami-Itabashi on the Tōjō main line, roughly following the route of today's Kanpachi (Ring Road 7) avenue. The name "Nishiita" combined Nishiarai and Itabashi. The link was intended to join Tobu's two otherwise separate networks so that rolling stock could be transferred efficiently between them and through services could be operated. An application for the licence covering the Nishiarai–Kami-Itabashi section was filed in November 1922, and the licence was granted in May 1924.

The full Nishi-Ita Line was never built. The Great Kantō Earthquake struck in 1923, between the licence application and its grant, forcing Tobu to prioritise repairing its existing lines. Bridge designs could not be finalised because the embankments of the Arakawa Drainage Canal, then under construction, were incomplete, and the cost of spanning both the Arakawa and the Sumida rivers was high. Local officials along the planned route pressed for rerouting, and as the late-Taishō and early-Shōwa years saw the area rapidly urbanise, construction costs rose and the prospect of profit faded. Only the short Nishiarai–Daishimae stretch, where land had already been secured, was actually completed, opened to carry pilgrims to the Nishiarai Daishi temple.

This section opened on 20 December 1931 as the Nishi-Ita Line, running 1.1 kilometres from Nishiarai to Daishimae with passenger service. The grander plan was then dismantled piece by piece: in July 1932, the year after the opening, the company abandoned the planned construction between the Shikahama (Kōhoku) area and Kami-Itabashi. For the remaining Daishimae–Shikahama segment Tobu submitted a request to extend the construction deadline, but this was rejected in June 1937 and the licence lapsed. Because the connecting line was never finished, Tobu's eastern (main) and Tōjō networks remain unjoined to this day; rolling-stock transfers between them are routed over the Chichibu Railway instead.

During the Second World War the line's operation was suspended entirely from 20 May 1945. Service resumed on 21 May 1947, and at that point the line was renamed the Daishi Line, the name it has carried ever since. The branch settled into its role as a short feeder to the temple and to the Isesaki Line interchange at Nishiarai.

On 1 December 1968 Daishimae Station was relocated to make way for the widening of the Kanpachi avenue, and the line was shortened by 0.1 kilometre to its present 1.0-kilometre length. On 26 July 1991 the line was elevated onto a viaduct, except in the immediate vicinity of Nishiarai Station. The elevation removed every level crossing on the line, making the Daishi Line the only Tobu route with no level crossings at all along its entire length.

One-man, driver-only operation began on 19 March 2003, after which a single two-car train normally shuttles back and forth along the line; services run about every ten minutes for most of the day, stretching to a maximum of fifteen-minute intervals in the early morning and late at night, with extra trains during the first three days of the New Year for temple visitors. Station numbering was introduced across all Tobu lines from 17 March 2012, the Daishi Line stations taking the "TS" prefix. For decades Daishimae had no ticket gates or machines of its own — fares were handled at a dedicated barrier within Nishiarai Station — but on 1 March 2026 ticket gates, ticket machines and fare-adjustment machines were newly installed at Daishimae and the Nishiarai connecting arrangement was discontinued.

• 1922November: Tobu Railway applies for a licence for the Nishiarai–Kami-Itabashi (Nishi-Ita Line) connection.
• 19245 May: the railway licence is granted for the Nishiarai-village–Kami-Itabashi-village section (steam power).
• 193120 December: the Nishiarai–Daishimae section (1.1 km) opens for passenger service as the Nishi-Ita Line.
• 193222 July: Tobu abandons the planned construction from the Shikahama (Kōhoku) area to Kami-Itabashi.
• 1937June: the request to extend the construction deadline for the Daishimae–Shikahama segment is rejected and the licence lapses.
• 194520 May: operation of the whole line is suspended during the Second World War.
• 194721 May: operation resumes and the line is renamed the Daishi Line.
• 19681 December: Daishimae Station is relocated for the widening of Kanpachi avenue; the line is shortened by 0.1 km to 1.0 km.
• 199126 July: the line is elevated onto a viaduct (except near Nishiarai), removing every level crossing on the line.
• 200319 March: one-man (driver-only) operation begins.
• 201217 March: station numbering is introduced across all Tobu lines; Daishi Line stations take the 'TS' prefix.
• 20261 March: ticket gates, ticket machines and fare-adjustment machines are newly installed at Daishimae, ending the Nishiarai connecting-gate arrangement.