Working remotely on a temporary visa

Hello! I have currently have a job in the US (computer engineering) that I love very much and would rather not leave. I also have a girlfriend in Toyama, and the long distance is rough. My boss is okay with me working remotely on and off a few times throughout the year for a month or so, since it only requires a computer and an internet connection. This would be ideal, as there really isn't a lot of work in the Toyama area in my field.

I've been researching the visa procedures for Japan, and I'm a little confused about what is and is not permissible on a temporary visitor visa. On the one hand, it says you are not allowed to work in Japan, but it also says it covers temporary business travel, which makes me think "working in Japan" might refer to earning money via Japanese companies. Does anybody know where the line is drawn on this one? Do they look askance at (or deport) you for working for your home company in your hotel while you are abroad on a temporary visa for personal reasons?

How would they know? If you're working in a hotel room remotely and getting paid in USD by a foreign, non-Japanese company, how would they know you're "working" in Japan? I think you're overthinking this whole thing.

My bigger concern would be how many times a year you'll be in Japan on a tourist visa... that might draw more scrutiny from immigration than the possibility that you're getting money from an overseas company that doesn't have anything to do with Japan.

I can only think of one thing that would look suspicious. Showing up at the airport with your desktop pc and a couple of extra monitor. If you just need a laptop to work then just come and work. No one is going to bother you. You are not even bringing your salary into japan so there is no way they'll find out you are working. And honestly, as long as you respect your visa terms they don't really care about what you are doing.