It is the terminus of the 47.5 km (30 mile) Seibu Shinjuku Line, which extends to Hon-Kawagoe in Saitama Prefecture.

Seibu planned to use right-of-way south of Seibu-Shinjuku Station which had originally been used for a streetcar line connecting Shinjuku to Ogikubo.

In the late 1950s and early 1960s, Seibu planned to extend the line to a new terminal on the second floor of the building now known as Lumine Est on the east side of Shinjuku Station, but this plan was eventually scrapped due to insufficient space to handle trains longer than six cars.

[2] Seibu was also a bidder to acquire the former JR freight terminal site in 1989, where they planned to build a new underground terminal; Takashimaya won the bid and constructed the Takashimaya Times Square complex on the site.

[3] It lies approximately 500 m north of the main Shinjuku Station complex, and is connected via the "Subnade" underground shopping street.