Moving to Japan is a nice dream, but you now need to move from the dream phase to the planning phase. Your first problem is a huge bureaucratic hurdle: you need to have a visa to live in Japan.
You can travel here as a tourist easily, but to live here as a resident you need to arrange a visa, and the requirements are quite stiff. Japan doesn't open its arms to anybody who wants to immigrate to Japan. (Actually, no country does this anymore, but I digress). Being genuinely interested in the country, and being sincere in wanting to learn the language are not valid qualifications for a visa. Usually you need to have a work visa (which comes, somewhat paradoxically, after you have secured employment in Japan). You need to think about what skills you might bring to Japan that would cause a Japanese company to take notice. There are other categories of visa besides work visa: student, artist, refugee, etc., but I think for practical purposes you ought to be looking at the requirements for a work visa. Alas, there is no visa category for the foreign Japanophile who seeks to buy a plot of land in the Japanese countryside and scratch out an existence there, although having just written that sentence I think it might be something the JP government ought to consider.
Becoming an English teacher is the lowest-hanging fruit for those who wish to work in Japan. But while this may be an interesting option for a gap year, most people find it difficult to build a career from it. If you love teaching and have qualifications, or are keen to pursue those qualifications, there are opportunities to teach outside of the English conversation schools (or, for example, start your own English-related business). If this isn't your bag, you will find the English conversation-school "teacher" to be a very tedious existence. It will be a survival-level existence. And, I suppose I don't need to tell you this, but there is a world of difference between living and surviving. Living in Japan is a nice, romantic dream. Surviving in Japan is as dreary an existence as it would be anywhere. There is nothing magical about Japan that makes "survival" here any more romantic than it would be in, say, Woolongong. This is especially true if you are intending to bring your partner and your kids here. Living in a drafty, damp, six-tatami-mat apartment, lit by one doleful fluorescent tube gets old pretty quickly. So get your career aspirations sorted first, and then figure out how to bring those to Japan.
The trick is to come to Japan prepared to succeed at something. And in the worst case - that is to say if you find out that Japan isn't your cup of tea - you can take your skills to another location.