I want to live there temporarily to improve my Japanese language skills and experience something different
Japan's culture and history is the opposite of Australia's in many ways, but has enough Western influences to still be comfortable and familiar enough, I think.
I think the main problem with otaku dreaming of living in Japan is that it's difficult to be realistic about a place you've only seen in pop culture media. Just like people coming to Australia thinking it's all koalas, kangaroos, surfing and Steve Irwin! It's not a correct or complete representation of the country as a whole, and certainly not of the day-to-day lives of people living there, so if people move to another country with that impression they're bound to be disappointed.