That's an interesting observation since when I were in Tokyo at peace time, many people did wear masks. It's also important to remember that basic sanitary and hygiene are also important which I'd like to believe that the Japanese are better than probably the rest of the world.

The difference is that maybe South Korea is in "panic mode" and Japan is yet to get there. They are less than half of Japan population and had 10 times more new cases in the last 24 hours.