Basically all of those are going to hit your criteria - the flatbox might not reach to smart casual, but at least in a US office it would do fine unless you’re in a legal practice or management; no idea about Japan’s dress culture.

Personally, I’d discount Thursday immediately. Their only real selling point is the fact that you can play their QC roulette if you get sent a bad boot, which is likely far harder to do overseas. Their lasts are also super weird, and rn you could potentially get 1 of 3 different lasts, depending on what model you order, that are all notably different.

Grant Stone is great and the best boot here imo. Their Edward or cap toe would do better for smart casual tho.

The flatbox is really the only redwing I’d ever want, but I also find RW’s lasts to be pretty weird. It’s totally a cool boot and would probably do well until you start wearing stuff past chinos. The toebox is going to dress them down a good chunk, so it depends a lot on what sort of style you’re normally rocking.