On maps, diagrams and signboards, the line is shown using the color silver, and its stations are given numbers using the letter "H".

[3] On maps, diagrams and signboards, the line is shown using the color silver, and its stations are numbered with the prefix "H".

Called "Line 2" at the time, it was designed to connect Naka-Meguro in southwest Tokyo with Kita-Koshigaya in the northeast.

The full northeastern extension of the line was never built, as the Tobu Railway upgraded to quadruple track within the same corridor to meet capacity demands.

[9] This was something of a coup for the Teito Rapid Transit Authority (the predecessor of today's Tokyo Metro), as the Toei Asakusa Line, which was also to be completed in time for the Olympics, had fallen behind schedule and remained under construction for the duration of the Games.

[10] The line, station facilities, rolling stock, and other assets were inherited by Tokyo Metro after the privatization of the Teito Rapid Transit Authority (TRTA) in 2004.