Question Questions about my koseki

I had a question regarding my koseki, I was adopted by an American family and removed from my japanese family's koseki. Neither me or my family have renounced my japanese citizenship, and was wondering if I have a koseki in order to get a japanese passport. I was told before that if you are removed from your parent's koseki then a new one would be created with just you on it, but wanted to make sure that this was the case. If I did have a koseki with just me on it, would I be able to retrieve it without my American parents' presence, as I have an expired passport with my kanji name, as well as my registered domicile.

If you are over 18, you should be able to apply for a new Japanese passport without having to tell anyone. You will need some form of birth certificate, so I suppose if you are in the US, the Japanese embassy will want to see a copy of your koseki. I don't think you will be able to retrieve a copy of your koseki remotely. You would need to check with the city/ward office of your last domicile to see what they require. Nowadays the ward offices of Tokyo allow to get copies of your koseki through a machine (sort of like an ATM machine, but one that prints out official documents). I think most major cities/wards have this system. If your last domicile was a remote or rural location, it probably has a much more analogue system of recordkeeping. Anyway, if you are over 18 you need not worry about your adoptive parents finding out - its the bureaucracy you have to worry about.

I haven't heard about the situation where you describe (adopted kids having an independent koseki set up for them). I'll dig around a bit, but I couldn't find anything when doing a quick search.

I asked the question on this website, (Obtaining japanese passport without koseki). Not sure if you feel completely safe clicking the link but the title is "Obtaining japanese passport without koseki" on japanguides.com. Someone sent a post that mentioned that when you're removed from a koseki, you have an independent koseki set up for you. Just wanted to get a second opinion with someone else to see if the independent koseki thing is true before I try to retrieve my koseki.

養子縁組の手続と国籍・戸籍の変動
国籍の変動：
養子が養親の国籍を取得するか否かは、養親の本国法によります。
２）養親が外国人の場合で、養子となった日本人が養親の国籍を取得する場合には、養子の日本国籍は当然には喪失せず、重国籍者となります。

As explained above, you would still have Japanese citizenship, so whether you have an independent koseki or not, it would not be impossible to get a Japanese passport, I think.

Would you be able to send the link to where you found that? I'm definitely less knowledgeable on the subject than you, but I'm not too sure how I would be able to prove my citizenship to a passport agency.

I already linked the page. You can see the page of an administrative scrivener's office by clicking the last line of my quote(the red one) in my previous post.

Oh, my bad, didn't notice that there. Thanks!