If you have enough funds, try applying for Humanities Visa
http://www.juridique.jp/visa3.html#selfsponsor
http://www.jiosu.com/geos-support-forum/geos-teachers/work-for-yourself-by-self-sponsoring-your-visa
check out the link I've posted. Basically it is what they call "Self-sponsored Visa" and you need to prove you can support yourself while living in Japan.
Other requirements can be found at the Japanese immigration website, check them out too.
Vacationing and actually living in Japan is totally different. A lot of foreigners ended up hating or loving the country. But as you said , its your dream. Go for it.
