That was to be expected. Japanese investors and businesses will shift their assets back into the Yen in order to help/bank on the rebuilding process, thus the rise in currency value.
The country is not bankrupt, destroyed or at war. They have money in the bank but even that is not important. The destroyed infrastructure is insured so the owners don't even have to pay out of their pockets. Especially true for businesses. The same as with almost every developed country with some brain. As such, there will be lots of business opportunities to be had in the construction and logistics sphere. Also for lots of cheap labor from neighboring countries.
central banks control currencies. investors don't have that kind of money to move it central banks ownz joo
Because of the insurance companies. Most of their assets are in foreign currency and now that they have to pay everyone they are switching them to yen hence rising its value.That and speculations.