If you'll have a laptop, you can print to most (any?) 7-11 locations, which are literally just about everywhere, including inside NRT and, I believe, KIX:

http://www.sej.co.jp/services/print_online.html (Japanese only)

A4-size pages are JPY 20 each. You make an account and can then submit things over the internet to print. When you get to the store, just enter the confirmation number you got and the printer/copier/ticket/everything machine will spit out your document.

Let me know if you need help getting through the website.

Alternatively, you should be able to use electronic boarding passes at NRT and KIX, but I'm not sure if TG offers these. I know NH and JL both do.