Turning Japanese no simple process

This is taken out of an article by Arudo Debito in the Japan Times :

If you can tolerate this degree of third degree, and don't mind giving up your original citizenship (Japan is the only OECD country which forbids dual nationality), then things become surprisingly easy.
This is a gross misinformation. Among the 30 member countries of the OECD, several forbid dual nationality and more restrict it. Have a look at the world map of dual nationality. Denmark and Belgium strictly prohibit dual nationality like Japan and South Korea, but most other European countries also generally prohibit it (Germany, Austria, Czech Rep., the Netherlands, Spain, Norway, Iceland, Finland, etc.).

Among the 30 OECD members, no less than 12 countries don't recognise dual nationality, which means almost half of them.

It is rather strange inside the EU, as dual nationality already exist for all EU citizens (everybody has the European nationality since 1992). I am in favour of dual (or even triple) nationality and I find it a pity that so many European countries don't accept it.