Many places in Miyoshi only take cash, so having some Yen is essential for local travel. For larger fees (such as for hotels and tours) one should be sure to ask beforehand if credit cards are accepted if looking to pay with such.
Getting Yen cash can be a slight inconvenience for some people. Firstly, the only foreign money exchange service is at Awa Bank in central Ikeda, though results have been mixed, especially with anything other than US dollars. There is no other exchange for foreign cash in Miyoshi, so one must go to larger Shikoku cities for this.
ATM machines that accept foreign cards are also somewhat limited here. The place to go would be a JP Post Office to use their ATM, which has English service and takes many foreign cards. Do note that not all post offices have ATMs, but there are several throughout Miyoshi including Oboke, Koboke, central Nishi-Iya, and two in Oku-Iya (Kyojo and Ochiai). Also, postal ATMs have limited and mixed hours (especially weekends), and are usually closed in evenings. In Oboke and in Ikeda there are a few convience stores (7/11, Lawsons) which have foreign card ATMs in English and other languages, and available 24 hours. (There are no convenience stores with ATMs within the Iya Valley, only Postal ATMs).