I mean, if your post said you had been thinking of making an international move and exploring options for a while, instead of jumping immediately to throwing your citizenship away, I could've pulled out one of the hundred responses I've given on this question before. Your post was just so extreme, and honestly sounded like you hadn't really started the journey of understanding how to make a living here yet, that I just wanted you to pump your brakes a bit. As for what you think you know about living costs here..again, I think you need to slow down and research a bit. Especially about actually buying property and what that entails.
Where exactly would you like to live? What kind of lifestyle would you like? Your career options also fit into this question. If you just want non-skilled work living in a 1DK, come on over man. Not sure how that fits into 'saving' and 'life pursuits' though.
Edit--
Also the whole Brexit..Trump..god damn millenials thing.. you have to understand that these are not automatically cured in Japan. There is a generation of young people here. They too are incredibly non-active and unmotivated in a lot of areas. They too waste their energy and lives on stupid things. The work and schooling culture here is absolutely brutal for young people. How up to date are you on Japanese politics? Japan is in a very sensitive spot right now with how Putin and Trump are going. Abe has a very fierce plan that he's trying to pull off. Hell, even the shit with Koike, her predecessor, and the Olympics is just a tiny glimpse into how things are run here.
You're an adult obviously, I don't need to tell you to avoid the grass is greener mentality. If things like the movements of young people affect you that much, how will you deal in a country where you have no cultural or linguistic understanding of what the people around you are doing? Or is it enough to just say 'well, it's not my country, so whatever'? Which wouldn't make much sense if your goal is to actually be a citizen of the country.
Seriously, not points to dissuade you. Come, man. It's a great country. Just trying to give you points to think about, mull over.
OH - AND COME TO THE THREAD ---
http://www.neogaf.com/forum/showthread.php?t=1206948