5. Blow your nose in public
Take the metro in Tokyo in winter and you will enjoy a nose-sniffling concert. Japanese people hate to blow their noses in public, or worse, see someone blow theirs. In fact, sniffling is perfectly normal in Japan, and serious snorting goes completely unnoticed. People walking around with runny noses or snorting it all back in are, unfortunately, not rare. Believe me when I say that, more than once, I fought the urge to hand out a pocket pack of Kleenex to someone sniffling and say: “Just go ahead and BLOW IT already!”