Yotsukaidō is a city located in Chiba Prefecture, Japan. As of 1 November 2020, the city had an estimated population of 95,266 in 43,191 households and a population density of 2800 persons per km2. The total area of the city is 34.52 square kilometres (13.33 sq mi).

The Sōbu Main Line is a Japanese railway line operated by the East Japan Railway Company in Japan. It connects Tokyo with the east coast of Chiba Prefecture, passing through the cities of Funabashi, Chiba, and Chōshi. Its name derives from the old provinces of the area which it serves: Musashi, Shimōsa and Kazusa. Its official line color is navy.