Best way to transfer money to bank in Japan?

My wife and I live in the USA, but she is Japanese citizen with a bank account in Japan. We are wanting to transfer money to her account in Japan but don’t want to pay huge transfer fees. What is the easiest and I guess the CHEAPEST way to transfer money from the US to Japan?

Bank of America will let us change $ to yen at no charge but then that would require us bring large amounts of cash with us each time we visit and depositing it when visiting in person. Not sure if there is an easier way in this day and age?

Thanks