... gave me her JPost Bank account number. As I will be travelling to Japan for a short trip, I was thinking of paying her by depositing the amount to her JPost Bank account.
...Could someone help me? Do I just go to any JPost office in Hakata and quote her bank account number?
Banking in Japan is quite different to some other countries. You cannot just walk into the branch, fill in a deposit form, and deposit cash free of charge into any account at that bank.
There are different ways of transferring money into Japan Post Bank accounts.
At the Post Office, you could do a Denshin haraikomi transaction, as described here:
http://www.jp-bank.japanpost.jp/kojin/tukau/sokin/koza/...
525 yen if under 30,000yen
735 yen if 30000yen +
If you have your own Japan Post Bank account, you can currently transfer funds free of charge into other Japan Post Bank accounts using Japan Post Bank ATM and Internet Banking.
I'll be in Hakata, but her account is opened in Nagoya.
Not relevant.