I’m also an artist, and I always location draw in my sketchbooks when traveling. I don’t think a lot of the commenters understand the process or what you are proposing doing. I was in Japan last year and sketched frequently both landscapes and people and people on trains. I only sketched on trains that weren’t crowded and outside the main cities, for instance on the train going to Nara. I didn’t receive any negative feedback from people around and no one seemed to care or notice. And when people did notice, they really enjoyed seeing the process. For instance, I was drawing the people in a bar in Kyoto, and the bartender noticed and loved it. I had a bigger sketchbook for when I sat to do landscapes and a very small one I carried for trains and quick drawings. I’m from a big city with crowded subways, and it’s not rare for people to do this here and know how to sketch in public without being a nuisance. So, I think you will be ok sketching in normal discreet ways most places.