Tokyo is made up with a spaghetti of subway
lines. It is often confusing even to the locals, but it does get you to
where you want to go. Tokyo itself actually has two separate subway
The TOEI system is run by the municipal
government and has 4 lines.
The Tokyo Metro has 9 lines and is a consortium
of railroads and governments.
The two systems do have interchanges, but have
different fare structures. A PASMO or SUICA Farecard is the way to go.
To transfer you must tap your Farecard to exit one system followed by
entering it another turnstile to enter the other. Both systems are
working on expanding their lines.
The Toei O-Edo Line is the biggest expansion
forming a ring around Tokyo to provide some relief for the JR Yamanote
Line, and the new Metro Fukutoshin line parallels the Yamanote line,
also providing some relief.