[belorn]

In Japan, how long can you keep a minimum distance of 1,5 meter or greater to any other human being while outside your home? Japan is not exactly known for its low population density, nor having a young population.

I think most would agree that if they weren't effective in any situation then hospitals wouldn't had used them before the pandemic. The question has thus never been about if mask works, as obvious they do, but rather at what level of risk that they start being more effective than background noise.

If I traveled to Japan I would distinctly wear a n95 mask both on the plane (a small tube of recycled air with minimal distance to each other for a long period of time), and inside Japan when near people. I wouldn't however go out to work/school if I felt like I was getting a cold, even if culturally people would look down on me for missing work. I can imagine that the social pressure would increase the general risk and thus masks would be a useful mitigation tactic.