[Jidohanbaiki]

Is it better to exchange money at a bank before you go to Japan or when you are actually in Japan at the airport or something? (I'm in New Zealand if thats relevant)

At first I thought it would be better to exchange it at a local bank, but I remembered that there is a cost when getting foreign money, but no fee for changing it back because the bank wants more foreign money, so would that be the same for japan?