Seibu Railway Co., Ltd.

The second lineage — from which the present legal entity directly descends — is the Musashino Railway, founded on 7 May 1912, which opened Ikebukuro–Hannō, part of today's Ikebukuro Line, on 15 April 1915 and reached Agano in 1929. The developer Tsutsumi Yasujirō entered through his company Hakone Tochi (later Kokudo), which from 1924 sold the Ōizumi Gakuen development along the line and in 1928 founded the Tamako Railway. When Musashino fell into crisis in the early 1930s Tsutsumi bought up its shares and led its rehabilitation, absorbing the Tamako Railway in 1940 and becoming president; Hakone Tochi gained control of the (old) Seibu Railway in June 1943.

Wartime brought the two railways together in an unusual joint mission: from September 1944, at the request of Tokyo administrator Ōdachi Shigeo, they and the affiliated Shokuryō Zōsan ("Food Production") company hauled night soil out of central Tokyo in trains nicknamed the "golden trains" (last run 1951), after truck disposal collapsed amid gasoline and labour shortages. Against this background the Musashino Railway absorbed the other two companies on 22 September 1945 under the Land Transport Business Coordination Act, becoming the Seibu Agricultural Railway — renamed Seibu Railway on 15 November 1946, with the bus operations spun off into what became Seibu Bus.

Postwar recovery was distinctive: Seibu rebuilt war-damaged and superannuated national-railway cars at its Tokorozawa works, earning the nickname "the second JNR". On 25 March 1952 the Murayama Line was extended to Seibu-Shinjuku and renamed the Shinjuku Line; in 1963 Seibu became the first private railway in Japan to run 10-car trains; and on 14 October 1969 the Seibu Chichibu Line opened together with the 5000 series "Red Arrow" limited express — the 101 series, first of its signature yellow trains, debuted that March. After Tsutsumi Yasujirō's death in 1964 his third son Yoshiaki led the group, with Kokudo building Prince Hotels and resort businesses and acquiring in 1978 the baseball team that became the Seibu Lions; Forbes ranked Yoshiaki the world's richest man from 1987 to 1990. The stock was listed on the TSE First Section from 1957, but control stayed with the family through Kokudo. In 1986 the head office moved from Minami-Ikebukuro to Tokorozawa, Saitama.

The family era ended in scandal. In 2004 a sōkaiya payoff affair forced Tsutsumi Yoshiaki to resign the Seibu Railway chairmanship in April; on 13 October came the disclosure that securities reports had been falsified — Kokudo's holding under-reported by 22% and parked under 1,000-plus borrowed names, the top ten holders alone exceeding the TSE's 80% delisting threshold. The shares were delisted on 17 December 2004, and Yoshiaki was arrested on 3 March 2005. A sweeping reorganization followed under new president Gotō Takashi: Kokudo, recapitalized by investors including Cerberus Capital Management, merged into Prince Hotels on 1 February 2006, and the 3 February stock transfer created Seibu Holdings, the reorganization completing on 27 March with Cerberus the largest shareholder at 29.9%. Cerberus later proposed abolishing five lines — the Tamagawa, Yamaguchi, Kokubunji, Tamako and Seibu Chichibu lines — and mounted a hostile tender offer that lifted its stake to 35% by June 2013; the proposals were voted down, and Seibu Holdings relisted on the TSE First Section on 23 April 2014.

Today Seibu operates 12 lines totalling 176.6 operating kilometres, divided into the operationally separate Ikebukuro Line and Shinjuku Line systems, which cross at Tokorozawa. Via the Seibu Yūrakuchō Line, trains run through to the Tokyo Metro Yūrakuchō Line (from 1998) and Fukutoshin Line (from 2008), and since 16 March 2013 onward to the Tōkyū Tōyoko and Minatomirai lines, joined by the reserved-seat S-TRAIN in March 2017. The 001 series "Laview", the first new limited express type in 26 years, entered service on 16 March 2019; under a 2023 "sustainable rolling stock" programme Seibu is acquiring secondhand cars from Tōkyū and Odakyu, the first — the ex-Odakyu 8000 series — entering service on 31 May 2025. Wholly owned by Seibu Holdings and itself the parent of the Saitama Seibu Lions, Seibu Railway is headquartered in Tokorozawa; its registered head office is at Daiya Gate Ikebukuro in Toshima, Tokyo.

• 189421 December: the Kawagoe Railway opened the line from Kokubunji to a temporary station at Kumegawa (today's Higashi-Murayama) — now the Seibu Kokubunji Line — and extended it to Kawagoe (today's Hon-Kawagoe) on 21 March 1895.
• 19127 May: the Musashino Railway, the direct legal predecessor of today's Seibu Railway, was founded; the company marked its 100th anniversary on 7 May 2012.
• 191515 April: the Musashino Railway opened its line from Ikebukuro to Hannō, now part of the Seibu Ikebukuro Line.
• 192716 April: the (old) Seibu Railway opened the Murayama Line from Takadanobaba to Higashi-Murayama, double-tracked and electrified, and began through service between Takadanobaba and Kawagoe — part of today's Shinjuku Line.
• 194522 September: under the Land Transport Business Coordination Act, the Musashino Railway absorbed the (old) Seibu Railway and the Shokuryō Zōsan company and was renamed the Seibu Agricultural Railway, following the three companies' joint wartime night-soil transport operation for Tokyo.
• 194615 November: the Seibu Agricultural Railway was renamed Seibu Railway, the present company name, and its bus operations were spun off into what became Seibu Bus.
• 195225 March: the Murayama Line was extended from Takadanobaba to Seibu-Shinjuku and the line was renamed the Shinjuku Line.
• 196914 October: the Seibu Chichibu Line opened, and the 5000 series "Red Arrow" limited express entered service; the first of the company's signature yellow trains, the 101 series, had debuted on 5 March the same year.
• 19865 August: the head office moved from Minami-Ikebukuro, Toshima, Tokyo to Tokorozawa, Saitama Prefecture, where the Ikebukuro and Shinjuku lines intersect.
• 199826 March: mutual through services began with the Teito Rapid Transit Authority (now Tokyo Metro) Yūrakuchō Line via the Seibu Yūrakuchō Line.
• 200417 December: Seibu Railway shares, listed on the First Section of the Tokyo Stock Exchange since 1957, were delisted after the 13 October disclosure that securities reports had been falsified — Kokudo's shareholding under-reported by 22%, with shares held under more than 1,000 borrowed names; the exchange had decided on delisting on 16 November.
• 20063 February: the holding company Seibu Holdings was created by stock transfer, two days after Kokudo was merged into Prince Hotels and one day after Seibu Railway became a wholly owned subsidiary of Prince Hotels by share exchange; the group reorganization was completed on 27 March, leaving Seibu Railway a railway-focused operating company, with Cerberus Capital Management the largest shareholder in Seibu Holdings at 29.9%.
• 201316 March: mutual through services began via the Tokyo Metro Fukutoshin Line (joined in 2008) onto the Tōkyū Tōyoko Line and the Minatomirai Line; the same year Cerberus's hostile tender offer raised its stake in Seibu Holdings to 35%, but its restructuring proposals — including abolishing five unprofitable lines — were voted down, and Seibu Holdings relisted on the TSE First Section on 23 April 2014.
• 201916 March: the 001 series "Laview", the company's first new limited express type in 26 years, entered service; it won the Blue Ribbon Award on 5 June 2020.