Cancelation of your registration
When you move back to Belgium or to another country you have to notify your departure to the Embassy of Tokyo
For registered Belgians (excluding status: Unregistered) a certificate mentioning the end of your consular registration can be delivered (upon payment of consular fees).
If you return to live in Belgium you will have to register with the city administration; this is compulsory. Your registration with the Embassy in Tokyo will be automatically cancelled. The same applies if you move to another country and request for the registration at another consulate, which is not compulsory but highly recommended.
You’ll find more practical information for your return to Belgium on the federal portal site.