If you are living in Japan (or even if you are just visiting), it is a good idea to register at your country’s embassy. This will allow the embassy to help you establish communication with your family in case of a large-scale emergency such as an earthquake or tsunami.
The Canadian government has recently updated its system for letting Canadians register their trips abroad. They now let you set up an account so you can update your information yourself instead of re-registering from the beginning every time something changes. They might still keep the data from people who registered through the old system for a while, but it would be better to register yourself in the new system as soon as possible, just in case.
For future reference, contact information for the Canadian Embassy in Tokyo is:
7-3-38 Akasaka, Minato-ku
Tokyo 107-8503, Japan
(If calling from abroad, add the country code (81) and take off the first zero.)
Some of the other embassies should offer similar services. (If you know of a system like this for your country, please post it in the comments.)