What I don't understand is how a move to 0.25% is triggering the trade to unwind. Is the carry trade based on the delta between US rates and Japanese rates? If so there is still a pretty big difference between the US and JPY rates so why now? I'm sure there is nuance I'm missing.
The change might seem insignificant, but it basically means that the borrowing cost more than doubled. It's akin to being able to pay $2,000 a month for your mortgage, but now, with a rate change, your mortgage is $4,000 a month.