The Tokyo Metro Tozai Line is a rapid transit line in Tokyo and Chiba Prefecture, Japan, owned and operated by Tokyo Metro. Its name translates to "East-West Line". The line runs between Nakano in Nakano-ku, Tokyo and Nishi-Funabashi in Funabashi, Chiba Prefecture. The Tōzai Line was referred to as Line 5 during the planning stages; the seldom-used official name is Line 5 Tōzai Line . The line carries an average of 1,642,378 passengers daily (2017), making it the busiest line on the Tokyo Metro network. On maps, diagrams and signboards, the Tōzai Line is shown using the color "sky blue" and its stations are given numbers using the letter "T".

Takadanobaba Station is a railway station in the Takadanobaba area of Tokyo's Shinjuku ward, situated between the commercial districts of Ikebukuro and Shinjuku.