Yen, ATM and credit cards
In Japan, the Yen (pronounced En) is used. Currently in circulation are the 1, 5, 10, 50, 100 and 500 coins and the 1000, 2000, 5000 and 10000 banknotes. You can easily change Euros into Yen here in Italy before you leave, at a bank or post office, obviously ask first about the exchange rate and whether there are any commissions. Absolutely avoid the currency exchange kiosks usually found at airports and in Italian cities. The exchange rates at Japanese airports, on the other hand, are good and have no commissions.
The yen-euro exchange rate can fluctuate a lot over the years, from a recent high of 96 in 2012 to a low of 165 in 2024.
With the ATM (Maestro/Cirrus circuit), you can withdraw from the ATMs of the Japanese post office, Seven Bank, E-Net (Family Mart), Lawson ATM, AEON Bank, Mizuho Bank and Bank of Tokyo-Mitsubishi UFJ. However, do not rely solely on ATMs, as some older ATMs do not read microchip ATMs.
Major credit cards are also accepted. With a credit card, however, you are better off withdrawing a certain amount of banknotes, given the rather high fees you will be charged. One thing should be noted, however. The Japanese much prefer paying in cash and snub credit cards a bit.
One solution is to apply for a credit card that gives the possibility of having accounts in different currencies. For example, you can apply for the Wise debit card, which allows you to load Japanese yen (or 50 other currencies) into your account with a very advantageous exchange rate and very low fees. Once the money is loaded onto the card, it can be used to pay directly in shops in Japan, without any additional fees. There is also the possibility of withdrawing up to an amount of 30000 Yen per month, unfortunately, being a foreign card there will still be a fee of 110 Yen (for withdrawals up to 10000 Yen) and 220 Yen (for withdrawals from 20000 Yen upwards), above the limit commissions of 1.75% and 70 Yen will be applied to each withdrawal.
Eclipse2009, Public domain, via Wikimedia Commons
So my advice is to make an estimate of how much money you will need on the trip (to pay for transport, hotels, restaurants, gifts, etc.) and have it in cash. Then you can do as I did, I brought along a rechargeable credit card (like Postepay) with some money in it in case of need. Finally, I recommend the XE site on which you will find the valuation of all world currencies in real time.