When you are naturalized in Japan, you need to abandon your nationality.

When you are naturalized in Japan, you need to abandon your nationality.
This is because Japan does not recognize dual citizenship.

Therefore, foreigners who are allowed to naturalize must declare their choice of Japanese nationality.
Specifically, this is done by selecting the Japanese nationality and submitting a "nationality selection notification" to the effect that the foreign nationality will be abandoned at the municipal office where you live.
It should be noted here that submitting this "nationality selection notification" does not mean that you will naturally lose your nationality.
It is necessary to confirm with the embassy of your home country in Japan whether you will lose your nationality.
If you do not lose your nationality, you will need to go through the loss procedure. 

If you are thinking of naturalization, please feel free to contact us.