No doubt. I don't think that's the concern. This is a really big bank, with lots of assets. How many smaller banks are in the same situation?  We saw the start of it last year. Those safe US bonds aren't so far at these interest rates. 

siggy47

econ

Japan Bank to Overhaul Investments as Wrong-Way Rate Bets Trigger Bond Losses

While 63B$ sounds like a lot, I believe the markets will absorb it without much trouble. What leads me to think this way? The sale will be done gradually, and if central banks need to intervene, they are there. I do not underestimate the power of central banks to print money.