Children who is born from an Australian citizen in Japan needs to apply for their citizenship at Australian embassy in Japan.
Japanese family register (‘Koseki Tohon’ – 戸籍謄本 or ‘Koseki Shohon’ – 戸籍抄本) is required to prove the relationship.
The document is written in Japanese so it should be translated and must be certified by a person with the appropriate authority. They must be:
an Australian citizen, or
if applying from outside Australia, a citizen of your country of residence if no Australian citizen is known to you
AND
have known you for at least one year
not be related to you by birth, marriage or de facto relationship
be easy to contact by telephone during normal working hours
AND
who is on 38 listed occupation by Australian government.
http://japan.embassy.gov.au/files/seol/17%2001%20-%20CBD%20checklist%20-%20ENG.pdf
Notary public, Judge of a court and there is a Legal practitioner on No 15
15. Legal practitioner (licensed or registered)
And it is including Japanese immigration lawyer like us.
We take care of the translation of Japanese certifications.