Otearai is another common term for 'toilet'.
Also, I was told that in Tokyo there may not be toilet paper available in the public restrooms, and taking along a packet of tissues (or collecting the freebie tissue packets offered as advertising by some businesses) would probably be a good idea. I hope this is no longer true, but, best to be prepared...
This is a very old site (1997), but an eye opener! I hope the bad ones have been cleaned up by now...ugh.
tokyo toilet map