DualNational to get Japan passport in US

So for anyone who's interested...
I was able to get through immigration without a hitch, I used my Japanese passport when entering Japan and altho I did not have a US exit stamp on my brand new Japanese passport, the lady at immigration didn't seem to think twice of looking and just stamped the Japan entry(or coming back) stamp on my Japanese passport. Got through immigration in probably less than a minute.
At customs, I had to declare that I had a few extra bottles of wine and when the customs inspector checked my passport, he noticed that I did not have an entry or exit stamp from abroad, and knowing that I was on a United Airlines flight from the states, he asked if I lived there, to which I answered yes. Didn't seem to be a major problem, he just told me to pay the custom fee for the extra wine, and I was on my way. So all went fine afterall.

Jeff:
As far as I'm aware, myself being born before 1985, it did not exempt me from the law passed in 1985 for not allowing dual citizenship. All materials I came across online and in print in regard to this issue, it seemed to say that the law still applies. Hence, I don't think your daughter will have a more complicated situation than what I had. From what I've read, I think she has to choose by age 22 her nationality. There is ONE thing that will be different for your daughter from my situation. For those who were born before 1985 and did not choose their nationality by age 22, the Japanese government assumes that you have chosen Japanese citizenship...so even though you may not explicitly sign any paperwork stating you choose one or the other, you will probably keep your Japanese citizenship. Now, for those born after 1985, I believe if you do NOT choose by the age of 22, the Japanese government will assume that you forfeit your Japanese citizenship.
I did not choose either nationality and myself being 26 now, I still maintained both nationalities and was able to get a Japanese passport issued. Perhaps there was a loophole that I jumped through without being aware of it. One thing that might be a good idea is to have your daughter get a 10 year Japanese passport made right before she turns 22 so she'll have that until she's in her 30's.

Apologies if this made things more confusing, but as long as she doesn't officially sign away her Japanese citizenship, she should be safe for a while. Good luck!

THanks for all your updates before and after the process i'm in the same situation as you, and this was a perfect answer, i simply want to know that when you submitted your old japanese passport did you get it back the same day? or did you have to leave it behind? Thanks for the info.

HI this is my first time to do this - but I couldn't help but share a few things I have learned on the way. If you know already, pls. 4 give me - if you are third generation Japanese/American (Japanese/Brazillian, etc) - you can apply for a nikkei visa to get you into Japan - you can work and do other stuff, but vote - more or less the same as a "foreign" person in the U.S. w/ a green card.

My friends & I often joke - that its moreso the mood of the person you are working with at the embassy than the actual rules.

My understanding is that the US doesn't care if you are dual - but more so Japan does. Although w/ the low birth rates - high suicide rates things seem like they may change.

Glad things are working out for you folks

If I remember correctly, I had to leave the old Japanese passport at the consulate. But, I got it back when I went to pick up the new passport. I think they stamped or punched holes in the old one, saying "invalid" or something along the lines of that. Hope that helps, good luck!