The hardest part would be getting the visa to do this, without a visa it's hard to get a part-time job, you can't have a bank account. Japan is an extremely strict company when it comes to your visas, the easiest option is to become a student; however if you are Canadian, Australian, and German(and a few others) you can come on working holiday for a year and do whatever you please. For me, I had the money so I opted into a language school which took care of my visa.

After that it's adjusting to the culture, and I'll go ahead and say Tokyo is completely different than the rest of Japan in terms of how people act towards you and how things are done. I believe it's the best starting point for anyone. I have a few others things I could say about this but I'll save that for another thread :)