The salaries in Japan arent great honestly, but mine, the quality of life and how far my money goes is so much better than if I lived back at the UK. Every time I go back it seems more and more people are struggling to pay for basic expenses - and even if I moved back it seems get a great salary I'd have to live in London, which I dislike.
I imagine lots of people far more talented than me must also be feeling the pull to not stay in the country too. Its festering politically and economically. Besides family there really is no benefit to remaining.
There's really no excuse for a country like the UK other than ordinary plain and simple mis-management from the top.
Singapore did not depend on neighboring countries to climb out of 3rd world poverty. To name an example.
In a similar situation to you apparently. Every couple of years I'll take a look at UK as well as NZ and Aus (all places I can legally work) and Japan is still the better option. Even with the yen situation and despite all the doom and gloom others write online, life is still pretty nice here.