[1] One envisioned purpose of the line is to carry Haneda traffic to and from central Tokyo stations such as Ikebukuro and Shibuya via the Tokyu network and the Tokyo Metro Fukutoshin Line.

[1] The new line is designed to branch off from the Tokyu Tamagawa Line near Yaguchinowatashi Station, and from there enter a 1.7 km tunnel which would include new underground stations at Kamata and Keikyu Kamata.

Ota City's proposal to address this issue called for the line to initially terminate at Keikyu Kamata, allowing same-station transfers between Tokyu and Keikyu trains at Kamata, and then to eventually offer through service to the Airport Line either by using Gauge Change Trains or by upgrading the Airport Line to dual gauge.

[5] The Ota and Tokyo governments agreed in 2022 to divide the cost of the line, aiming to commence operation in 2035.

[2] A third sector operating company, Haneda Airport Line, was founded in October 2022 with investment from Ota City and Tokyu.