History
The Seibu side of Nakai Station opened on 16 April 1927. A 1 November 1963 rebuild turned the original island platform into two side platforms flanking a central passing track, enabling express overtaking. A footbridge entered service on 16 November 1969, and automatic fare gates on 1 December 1992. On 19 December 1997 the Toei side opened as a stop on the Number 12 Line — renamed the Ōedo Line on 20 April 2000 — about 35 metres below Yamate-dōri. PASMO acceptance began on 18 March 2007. On 5 June 2016 the Seibu ticket hall moved underground, and a north–south free passage with a new north entrance opened on 17 December 2016. Numbers SS04 (Seibu) and E 32 (Toei) apply.
History summarized from Japanese & English Wikipedia · last reviewed 2026-05-18.
Notes
The Toei platform sits roughly 35 metres below ground beneath both Yamate-dōri and the Shuto Expressway Central Circular Route's Yamate Tunnel, with no direct underground passage to the elevated Seibu station above.