Issues concerning the civil status of a person (birth, lineage, adoption, name, marriage, divorce, decease,…). can be very complex. Questions related to civil status can not be answered by phone. Always submit your personal case in written to the Embassy of Belgium in Tokyo
The Belgian civil code is applicable to all Belgians, living in Belgium or abroad. You can read more on the website of the Federal Public Service Foreign Affairs. Since June the 1st 2014 a new law on the given names of a person is applicable. You can find more details on the following site (only in Dutch or French).