通貨 is the items in the game that can be used to buy other items in a shop. These are copper coins and gold coins.

The two types of coins are able to be exchanged for each other at a 100:1 ratio (100 copper coins for one gold coin) in either direction. This is done through a portal.

At a furnace, a gold ingot can be smelted into ten gold coins, and a copper ingot can be smelted into ten copper coins, as well as vice-versa.