J-Subway Cards All of the above - except the one from the Keio Line - are from the Tokyo subway system, but the subway cards can be used on the private railways in Tokyo and the cards from the private railways (such as the Keio card above) can be used on the subway lines.  It's quite convenient and a really great idea - each company used to have its own cards, which were not compatible with the other lines. Images Through Glass, Tokyo