Absolute orientalist BS.
I work in a Japanese workplace. Lots of people here don't normally wear masks. When they do wear masks, they pull them down to cough or sneeze so that they don't walk around with a wet and dirty mask. The idea that I could be dirty and infecting people doesn't cross the minds of most people, just like how in many places around the world people are taking international trips and dodging quarantine.
Recently, almost everybody is wearing a mask. People have jokingly asked if the new mask wearers are infected, to which they quickly reply along the lines of, "No way. I just don't want to get infected by you guys."
Japan isn't some society of honor and sacrificing oneself for the good of the country or whatever like movies based on ancient stereotypes make it seem. Most people are looking out for themselves just like anyone else. The way it's done is just sometimes different.