If I have a flight NYC-ORD with UA then connecting with a NH flight to TYO in one itinerary, and I want a second bag, I will have to pay for it in NY for UA when checking in. Will I have to pay for NH again for the second bag?
you only pay it once, from origin to destination (when its in 1 ticket)
What happens if the second carrier gives 2 free bags, but the first carrier gives only one free bag?
It goes according to the first.
Hmmm even if the first one is just a domestic 1 hour flight (AA) and the second is the the international (JAL)?