The Japanese Yen is Japan’s official currency, issued by the Bank of Japan. Its ISO code is JPY and its symbol is ¥, usually written before the amount (for example ¥1,000). Everyday prices are in whole yen — the old sen subdivision is not used in shops. International listings use JPY so yen is not confused with the Chinese yuan, which can share the same ¥ mark.
The same notes and coins are legal tender nationwide: Tokyo, Kyoto, Osaka, Hokkaido, Okinawa and smaller towns. You do not change money when you travel between prefectures. A hotel or tour desk may also show a pound or dollar figure as a convenience quote; that is not a second official currency.