There are multiple ways to send money from Japan to your home countries:
Bank transfers: Fill out a form with your receiving banking information and some other documentation, then pay a processing fee of ~2500 yen (at Japan Post) and wait 30 min to an hour. The transfer takes up to a week to process, and you may be charged additional fees by your receiving bank. Requires Japanese to fluidly navigate, as well as physically going to the bank. You will need to fill out this form every time you send money.
TransferWise: Newly popular with expats and easy to apply online. Fill out a form (one-time) with your details and other documentation. When you get a confirmation screen with the details of your transaction, you'll get information for a local account to send the money to. All that's left is to go to an ATM, send a furikomi, and wait about 4 days. Future transfers do not require you to fill out an extensive form again, just the transaction details. Fee is about 400 yen for sending money under 50,000 yen or 0.8% of the total if over 50,000 yen.
GoRemit: Popular with expats, it's been the traditional method of choice for sending money. Mail in a paper application with your documents. Once the account is set up, each time you send money the processing fee is 2000 yen, regardless of the amount sent. Similar process to TransferWise by sending a furikomi to a local bank account.