So I've been living in Japan for five years, self-employed, always paying my taxes and hoken bills, but never enrolled in the national pension system. All of a sudden I got this letter from the Japan Pension Service stating, in English (among other languages!), that I'm "required by law to enroll in the national pension system and pay contributions".
Of course I'd rather not, seeing as it's quite pricey, not to mention that I've already been paying towards my national pension account in my home country (which unfortunately doesn't have one of those bilateral deals, I forget what they're called, with Japan – so what I paid back there probably won't affect what I have to pay here) since as long as I can remember, and I don't exactly see myself staying here until I retire.
After a bit of googling, it seems like there's no way to wriggle out of this whole thing. So instead, my question is: when I enroll, is the Pension Service going to demand full back payments for the previous five years, plus interest? (Needless to say, this would amount to a fortune by my standards...) Some people claim they can't demand more than two years of back payments, others ten. Or will they be happy as long as I start making the payments from now on, after I enroll? Has anyone here been through this process and lived to tell the tale?