Bikaben:
I think Mike is trying to help you think in a more realistic way about Japan as a real place with real people, and about the real possibility of your moving there. I think, perhaps particularly on this forum, there are a lot of people who really really like/are obsessed with small elements of Japanese culture--martial arts/anime/manga etc, and in their minds Japan then becomes this big glorious ball of everything that embodies shiny kawaii goodness in the word.
Then those people apply to a program like JET to become a teacher. And then they get here, ready to enter a world of ninjas,
samurai, etc, where everything is exotic and fun. And after they arrive, it really is: for a couple weeks. But then they realize they are living out in an apartment in the middle of nowhere, with very few people who speak English around them. And they're having trouble getting internet at home. And there's no anime on the normal television. And they have to stand in front of kids 'teaching,' when they themselves, and certainly the kids, would much rather be doing other things. There's a big different between what Japan seems like when you have never lived in Japan and what Japan is like when you're living there.
With that said, living here can be great. There are amazing experiences to be had, but you have to be pretty tough and determined to overcome the bad things, and flexible enough to adjust to the many unforeseen good and bad things that will come your way.
Thinking about Japan and your own plans and what is required for language study in a realistic way, as opposed to an idealized way, will only improve your quality of life once you get here. Unless you just want something to daydream about, and maybe a place to be a tourist for a couple weeks. If that's the case, go on, more power to you. But if you really want to live here and learn the language--start acting like it.
ETA: Some recent examples: (pretty relevant to the Japanese experience for foreigners I would say, at least those out in the country)
Negative: This weekend, a really weird trash-like statue-like object was placed outside my front door. I moved it, and creepily, the next day, it reappeared. Thinking about going to the police now and hoping nothing new has been put there (already threw away the first object).
Positive: Up in Aomori, went to see a large, famous festival in hirosaki city. Afterwards, I couldnt find my car, so I asked a person coming back from the festival for directions. Instead, she walked me the 25 minutes it took to where my car was, all the while explaining the history of the festival, and, to top it off, she gave my sister and I a couple of beers as goodbye presents after safely getting us to the car.