Can I become a Japanese citizen?

[cranks]

Originally Posted by MMM

I don't know that they will mail it overseas. You may need to go there in person.

This is a very good thread, as I don't remember someone with this exact question before.

I believe if the child of a Japanese citizen is born outside of Japan they have 6 months to get the koseki touhon updated and can then get a Japanese passport. I am not sure if it the same within Japan.

The link says they do mail overseas, but yeah I'm not sure if the policy is the same across all the offices.

As for koseki, if one is born abroad, he/she will lose citizenship if birth registration(出生届) is not filed promptly(actually within 3 months.)
http://law.e-gov.go.jp/htmldata/S25/S25HO147.html
第十二条 　出生により外国の国籍を取得した日本国民で国外で生 まれたものは、戸籍法 （昭和二十二年法律第二百二十四号）の定めるところに より日本の国籍を留保する意思を表示しなければ、その 出生の時にさかのぼつて日本の国籍を失う。

http://www.moj.go.jp/ONLINE/FAMILYREGISTER/5-1.html
国外で出生したときは３か月以内。なお，国外で出生し たときは，この期間内に出生届とともに，国籍留保届を しないと日本国籍を失う場合がありますので，留意して ください。

People who were born in Japan to a Japanese mother are automatically Japanese citizens and will not lose their citizenship even if 出生届 is not filed. Their parents will be fined, but 出生届 should be accepted years after their birth if all the paperworks are there. So as far as I see it, there is no reason she's not a Japanese citizen. But I'm not a lawyer and even I can guess filing 出生届 30 years after birth can be tricky.

[cranks]

Originally Posted by superasiaone

I have my original birth certificate. Would I be able to tell from that whether she filed the koseki?

You will be on Koseki when your birth registration along with your birth certificate is filed. So if you have the certificate, your mom may not have filed it, but she might have had several copies, so we can't really tell. She can file it now though, even if she didn't do it back then. But I don't know if filing 出生届 30 years after birth is easier, or getting the citizenship as a foreigner whose mother is Japanese is. I would guess it the latter.