How can I purchase good yield property in Japan?

You need to submit purchasing intent document ASAP and pay the full sum in cash!

Mortgage opportunities depend on your nationality, income, your residency in Japan, your spouse (i.e. your wife is Japanese), visa status, etc.

And of course, each banks have their criteria and review process, so once you find property you would like to purchase, you need to write purchasing intent document that you will use mortgage and of course, from seller's stand point, they want to sell to buyer who can fully commit.

Bank mortgage application process takes ca. 3-4 weeks at least, so 
if it is good competitive property, it might be gone while you do mortgage process.