Hi trand! Nice to know there's another diabetic on the forum who's at least been to Japan! I've been there on a two week holiday twice and loved it (even during the second trip when the tsunami and earthquake occurred, I have not been put off going again in future)!
While I was over there last, I found that familiarising myself with the characters for "carbohydrate", which I commonly saw as 淡水化物 (tansika-butsu) on the food labellings, was a great help! I often got some decent grub from convenience stores - it still amazes me now that they're clever enough to have a label stating per serving on even their hot dishes that you can get heated up in the store!
While on the plane I had the Japanese meal considering I don't mind taking a guess at how much it'll be for the trip.
I hope you enjoyed your time there despite the in-flight issues!
My bigger hassle was getting my split doses of Lantus working okay despite the time zones but thankfully, it works out to be roughly like flipping the day over on itself! I'm still not sure if my body adjusted fully from doing so considering my morning became night and vice versa!