The 10-yr government bond yield in Japan is now around 0.5%, following an almost linear decline that started in 2006. The only way to rationalize buying 10-yr JGBs at 0.5% is believing that Japan will have a deflationary environment over the next decade and/or the central bank will absorb (or even monetize) the bulk of new issue bonds.
Moreover, these record low yields will do some serious damage to the Government Pension Investment Fund, which invests two thirds of its assets into local bonds. A significant portion of the population will tap the pension fund in the next 10 years. There will also be pain for Japan's insurance industry that now faces a nasty asset/liability mismatch.