I am going to Tokyo for at least a year during my paternity leave with my wife and staying with her family
I just finished reading through this thread and I've learned a few things already:
1.) Join Gaijinpot and read through their forums
2.) Buy the lonely Planet book on Japan
3.) Study the language and customs
I will get my working holiday and international drivers license... thinking about buying a car there as well, it seems like there's a stigma against buying used cars in japan as they are much cheaper than cars here even with much lower mileage!
Anyone currently living in Tokyo or will be there in spring? :P