At the end of Wednesday's morning session on the TSE, the Nikkei-225 stock index had added more than 388 points, or 2.3 percent, to 15,097 points. It was the first since January 2008 that the Nikkei average had topped the 15,000 mark.
The dollar's rise to the 102-yen level this week encouraged buying of blue-chip exporters, including automakers, Nikkei.com reported. In the morning session, more than 3.3 billion shares had changed hands on the TSE, with trading value totaling about 2.5 trillion yen ($24.45 billion).
Investors also were encouraged by the Dow Jones Industrial Average closing at record highs the previous day on the New York Stock Exchange, further raising optimism about the U.S. economy, as well as an impressive performance by Germany's Dax index.
In the early session Wednesday, the dollar was trading at 102.18 yen. On Thursday, the dollar reached a 55-month high of 102.44 yen in New York.
The greenback broke the 100-yen mark for the first time since April 2009 last Thursday in New York and went over the 102-yen mark for the first time on Monday in Tokyo.
Investors on the Tokyo Stock Exchange are encouraged because a lower yen makes Japanese goods cheaper and thus helps boost their exports. A lower yen also will help push Japan's inflation higher, needed to lift the country's export-dependent economy out of its years of deflation or falling prices.
The government of Prime Minister Shinzo Abe has made it its top priority to end deflation. The Japanese economy is the third-largest in the world behind the United States and China.
The government and the Japanese central bank have introduced numerous stimulus measures for an economic recovery. Last January, the Bank of Japan doubled its inflation target to 2 percent.
Investors also remain optimistic about the U.S. economy. Among recent developments, the U.S. job market has been showing strength with the number of Americans filing for jobless benefits falling to a five-year low last week.
Other reports have said the yen's decline in recent months already have pushed up the profits of Japan's exporters.
Some analysts say the yen could dip to 105 against the U.S. dollar as central banks in many countries cut interest rates, which in turn create demand for the greenback.