"Seibu Railway" was originally the name of a tram service between Shinjuku and Ogikubo, which was transferred to the Tokyo metropolitan government in 1951 and eventually closed in 1962.

At the time, night soil was generally transported by truck to Tokyo Bay and disposed of by dumping there, but the progress of World War II led to gasoline and personnel shortages which made this system unsustainable.

Tsutsumi became the controlling shareholder in Seibu Railway following the merger through his holding company Kokudo Corporation.

Seibu Railway had its initial public offering on the Tokyo Stock Exchange in 1949 but remained under the control of Tsutsumi through Kokudo.

[2] Tsutsumi registered Seibu Railway shares owned by Kokudo in the names of various affiliated individuals, often without their permission, so that the true ownership of the company was not readily apparent.

His holdings in Kokudo and Seibu led to his being deemed the "world's richest man" by Forbes magazine for four consecutive years from 1987 to 1990, with estimated net worth of $15–20 billion during the height of the Japanese asset bubble.

Cerberus Capital Management, an American investment fund, became the largest shareholder in Seibu Holdings with a 29.9% share of the new company.

[5] Cerberus had aimed to raise its stake to 44%, bringing it closer to an outright majority, but Seibu management engaged in a massive campaign to thwart the tender offer, including advertising within Seibu trains to passengers who owned stock.

At the June 2013 shareholder meeting, several proposals by Cerberus were voted down, including the election of outside directors and the abolition of non-core lines.

[6] As of June 2013[update], Yoshiaki Tsutsumi remains a major investor in Seibu Holdings through his 36% investment in NW Corporation, the second-largest shareholder in the company with a share of around 15%.

However, more recent trains have a blue colored line on unpainted stainless steel or aluminium bodies.

[10] Several Tokyu 9000 and Odakyu 8000 series trains (100 vehicles in total) are expected to be transferred from their original operators from 2024 in use primarily on Seibu's branch lines such as the Kokubunji and Chichibu lines, thus bringing down energy consumption as they replace some of Seibu's oldest vehicles.

Children (under 12 years old) are charged half the adult fare (including the barrier-free fee), then rounded up to the nearest 10 yen increment if paying by cash.