You have a different kind of short term rental, and you are there. 

It's good to put together a long-term plan, but I have never understood how someone with 0 properties is more worried about how to scale then how to build the foundation correctly.You are putting the cart before the horse.

We’ve been gathering information about the rental property market in Japan in terms of realistic expectations for yields, as well as a reasonable timeline for getting started and generating income to support our family. 

with todays rates one could get7 to 10% interest on that long term and then defer your Cap gains over a course of years.

If you send the security deposit disposition to the address they rented from you with ADDRESS SERVICE REQUESTED written in the area between the address block and stamp you'll get a postcard back with the details if the mail is forwarded. 

I currently have a long term rental in the Cincinnati area.

Once we have spent time identifying details that affect them, I am given permission to buy for them without them having to visit.

Any advice from a long-term STR/Rental Arbitrage investor?  

We primarily do short-term, but also do mid-term and long-term!

I'm Isaac from Southern California, passionate about real estate investing for the medium and long term.