Condensation only occurs when you enter a warm place from cold place. Just need to wait awhile for it to go away before shooting. That's what the local there will do. So, just enjoy your trip and post for us to enjoy when you are back.
Oh, bring more batteries and memory cards. Batteries tends to drain faster in colder countries.
To add on. If it really bothers you, or the difference in temperature is really big... like between -20 and 20 deg, you might want to bring along some ziploc bags. Before entering a warm environment from a cold one, place your camera with lens in a ziploc bag and seal it. Bring it into the room, and you will see the condensation form on the outside of the bag, and not on the camera inside the bag. After the temperature of the camera stabilizes, (maybe 10 mins?), you can take it out of the ziploc bag. And yes, you can keep the ziploc bag and use it over and over and over again.
which part of japan will u be checking out? tokyo is not that cold to worry abt condensation when u enter indoors. the air is pretty dry as well. but just in case, just leave the camera inside your bag when u go indoors and wait for the camera to warm up before taking it out.