For the last 3 months the Yen is losing on average around 1% per week:
Yet the 2-year bond yield is negative. You have to pay the government to take your money. The 5-year yield is 0.05%. This means after 5 years you get a total of about 0.25% interest. This is about what the Yen loses in the average day recently.
They are printing at a rate of 80 trillion yen per year and buying mostly JGBs. This has driven up JGB prices far into bubble territory. These yields are absolutely nuts. It is not natural. Only massive central bank money creation and bond buying makes these kinds of numbers possible. These are not free market rates. Sane people are not buying JGBs at these yields. The insane central bank must be the only buyer.
Bubbles always fail somehow.