Banknotes are printed at the Printing Bureau of the Ministry of Finance. However, to prevent counterfeit money, the printing method is not disclosed in detail.
All that can be explained here is that banknotes are printed on special paper with many colors and always have a "watermark" on them.
Coins are made at the Osaka Mint. There are five types of coins: the 1-yen coin, made of aluminum; the 5-yen, 10-yen, 50-yen, 100-yen, and 500-yen coins, made of a mixture of copper, nickel, and other metals.
However, the detailed manufacturing process for these coins has not been disclosed. The only explanation given is that coins are made by forming melted metal and then stamping it in a mold.