The official unit of Japanese currency is the yen. One dollar is equivalent to 112 yen as of 10/10/18. The idea of Japanese currency was greatly influenced by China. In China certain type of shells were used as currency before coins were invented. Today, as in the past, some Japanese coins have a hole in the middle, and it is believed that this is a remainder of those shells that also had openings (see the photo). In Japan today there are six types of coins (1, 5, 10, 50, 100, & 500 yen) and 4 types of bills (1,000, 2,000, 5,000, and 10,000 yen). The bill for 2000-yen is not common, but you may come across one from time to time, I guess it is just like the two-dollar bill in the U.S.
