A few hours later, around 7:00 pm New York time, or at midnight London time, Japan wakes up and the currency markets begin to move. This is considered the beginning of the Asian session.
Japan is the third largest center in the Forex market, it includes about 10 percent of the total volume of foreign exchange trading. Many of the world's largest banks and hedge funds are located in Tokyo. At this time of day, there is a high volatility of currency pairs associated with the Japanese yen.