as a joint venture between Mitsubishi, the Keihin Kyuko Electric Railway (which owned the right of way), and Seibu Railway (which controlled the land surrounding Kataseyama Station).

The company applied for a construction license on 6 October 1965, which was approved later that month. The line was built above the former Keihin Kyuko Expressway, Japan's first automobile-only road. Originally intended to host a conventional