[Kyousuke]

well you could de-naturalize yourself from your place of citizenship for that of another nation. you would need to take a naturalization test to work your way to being a citizen. also they wont naturalize you if you have an arrest record. you would also need to get a workers visa or something like that. just proof that your are verified to work in the country if your arent a citizen. thats what the Mexican Naturalization is like to become american citizens, i think it would be the same for japanese naturalization give or take.