I have no idea what documents you will need to travel with a newly adopted child. I imagine you can find some help from people who've gone through that on a specialist forum.

With regard to the airport security checks during your connection, I believe that there are still limits to the liquids you can carry through the security check. If you're with a baby, then baby formula and food is exempted from the restrictions (but will be screened). Medications are OK, provided you carry the prescriptions. Other liquids over 100ml will be subject to confiscation.
http://www.narita-airport.co.jp/en/s...faq/index.html