Turns out Japan isn't as open for foreigners as even I had thought. I took part in a careers fair last month. There I heard the international outreach chap from a supposedly internationally-minded university proudly proclaim that 4% of its staff are foreigners, 50% of whom are language teachers (so have no job security), and the other 50% are "permanent", where those who can't pass the standard written exam (in Japanese) are still called permanent but are actually on short-term contracts. Wow... (BTW "short term" in Japan means your contract may be terminated at the end of each year for no reason).
The fair had presentations from 5 people who had been sort of successful in Japan. Two had survived in Japanese companies and were clearly exceptional individuals, having reached full proficiency in Japanese in a single year as well as excelling at their jobs. What about mere mortals? The three researchers were slightly less remarkable individuals. One guy had risen to the heady heights of a boss at RIKEN, a place like JAMSTEC, running a group that was at least 50% foreign. Well done him. Another was a recently employed Assistant Professor who had landed his job after a postdoc in Japan, after some superhumanly persistent networking. The other one was ... me! Here's my talk. Preparing for this event I thought I'd worked out how we have survived in Japan: there are two of us which enables survival in a pincer movement kind of a way. But while giving the talk I discovered the real reason we are still here. As I spoke, the Europeans laughed politely in a kind of "Ah, British humour - must adjust brain to understand - 'ha ha ha'" way, while the Japanese in the front row were doubled-up guffawing into their face-masks and, despite all the odd things I'd said, greeted me afterwards with happy smiles and teasing comments.
General Douglas MacArthur may have called the Japanese a nation of 12 year olds, but I suspect he never managed to make any of them laugh.