✔ 最佳答案
Firstly, you should estimate how much you need and exchange Japanese Yen in HK first since administration fee in Japan exchange rate shop and banks are expensive.
If you find that the money you exchanged is not enough when in Japan, I suggest you to go to the ATM machine with the logo CIRRCUS/PLUS, you can get money there and only small amount of administration charge and the rate is according to the bank. e.g. For HSBC, the handling charge is HK$25 for each time to get (no matter how much you take). You can ask the bank in HK first.
Hope this can help!