John wrote:

>>> I don't think I would ever give up my original citizenship.
>> Which is? If it is Canadian or US, you won't have to give it
>>> up, really...
> 
> Maybe I spoke too soon. I'm not sure about the laws. 

I think (without having checked it thoroughly) that from a Japanese 
point of view you can't have double nationality, but they can't stop you 
form holding on to the passport, etc., of your home country or from 
having all the rights of a citizen of that country once you leave Japan.

All they can do is withhold those rights while you are inside Japan, so 
you would be able to go to the embassy of your home country and be 
treated as a citizen of that country in every country of the world 
except Japan.

Thats how I understand it from talking to people who've done it.

John