They don't have a big headstart on other countries, and if this is just the tip of the iceberg, they might not even be number one anymore.
Especially if you consider the diet, which is the only thing not terribly obvious ("wash your hands", really?), we'd be looking at countries like Switzerland, Iceland and Spain, all which have a significant difference from Japan. Never mind that one should look at those anyway, as Japan is by no means a freak outlier. On average, a lot of countries are close and/or are higher than the US, so the only reason why Japan is often targeted is the allegedly high occurrence of people over 100 – which seems to be somewhat exaggerated.
Generally, the countries with high marks in healthcare seem to be doing well (I know, that might be tautological, depending on what part of the statistics those high marks are derived from). Fish, soy and tea? Not so much. (Apparently you may as well mix it with skyr, toblerone and paella)
