I'm turning 18 in January and I was born in Japan. My mom is Filipino and my dad is Japanese. My mom brought me to the Philippines when I was 3 and I've been here for 14 years. I have a Japanese passport, but it has expired. I don't have a birth certificate here in the Philippines. My father wants to bring me back to Japan; how could the process go?
Citizenship of the Philippines is acquired by jus sanguinis ("by blood"), so the fact that your mother is Filipino automatically gives you citizenship of the Philippines (given your date of birth — rules have changed over time).
Citizenship of Japan is also acquired by jus sanguinis, though with a few additional conditions for people born abroad, which is not your case. Since your father is Japanese, so are you (for now, see below). The fact that you previously had a Japanese passport seems to confirm this.
So, at this time, you are indeed apparently a dual citizen of Japan and the Philippines.
According to the consular affairs section of the Embassy of Japan in the Philippines:
Until then, I suppose you should be able to get a passport by applying to the Japanese embassy. You need:
- to get the application form from them
- apparently a "family register" (koseki tohon)
- your expired passport
- proof of identity
- consent from both parents
- to pay a fee of 5200 PHP (5 year passport) or 7600 PHP (10 year passport)
You probably want to get in touch with them if you have any questions. You'll need to make an appointment anyway given the current situation with the Covid-19 pandemic.