Hey @Kathryn Kuo - fellow Japan-based investor here. My personal opinions below, with a lot of generalities. And with no intention of being a wet blanket...
In my experience, most US citizens invest in US properties, even when living in Japan. In my opinion, the primary reasons are financing and appreciation.
Generally, you're likely to have trouble getting financing for investment properties here. This is true even if you set up a business and establish a track record. RE loans to business usually require the business owner to personally guarantee the loan. So you're left with acquiring properties all-cash. But since J properties generally depreciate over time (not like properties back home which appreciate), the idea of sinking cash into a property that is worth less five years from now is not terribly appealing.
Like you say, then the question is what sort of yield can you get, and will it cover the deprication losses?
I have seen posts where investors seem to be having success with airBnb rentals and/or acquiring "akiya" or other extremely cheap properties. Acquisition costs are low, so easier to generate good yields. People are doing it, so presumably it works.
FWIW, I invested in Japan for a few years, but lack of rent growth, lack of appreciation, concerns about natural disasters, and just general lack of confidence in the J market led me to shift focus only to the US. Totally happy to meet up if you're in Tokyo to discuss REI.
Finally, i'll ping a few others I believe are active/interested in Japan properties and generally based here in Japan (sorry guys). - Dave
@Casey Maeda
@Zachery Hitchcox
@Daniel Mills
@Shu Matsuo Post