両親ともに外国人の子が日本で生まれた場合、日本国籍は取得できない？
Naturalization in Japan requires the applicant to give up their current citizenship(s) either before or shortly after, depending on the nationality, the naturalization takes place if the loss of nationality does not occur automatically. Although there are rules in place, Japanese government does not strictly impose rules for the naturalization process, as the exact process for each specific nationality depends on the Japan's international relations and agreements with the given country. Basic naturalization requirements also differ from person to person regardless of their nationality and depending on the applicant's current status in Japan. Unlike most other countries, the applicant does not have to have been a permanent resident to be eligible to apply for Japanese naturalization.
the applicant does not have to have been a permanent resident to be eligible to apply for Japanese naturalization