Getting out of MCO is impossible on any airline so I feel you there. With your trip to Tokyo, you really won't know which hub you should fly out of until a few days prior, so checking now won't do much good. So be prepared to get to any hub from ATL if taking United to Tokyo. That said, know all the flights into Japan. United has a flight from HNL to NRT and through GUM. So look at every city in Japan. Since they have a fabulous rail system, you can connect to anywhere once you get there. Don't forget to check both airports in Tokyo too, HND and NRT.