What kind of money did ancient Japan use?

In ancient Japan, the earliest forms of currency were barter and primitive coins made of shells and stones. Later on, during the Yayoi period (300 BCE - 250 CE), rice was used as a form of currency. It was not until the 7th century CE that metal coins, known as Wado Kaichin, were introduced in the Asuka period. These coins were made of copper, silver, and gold, and were used for trade and commerce.