The Japanese yen strengthened against the U.S. dollar, briefly hitting the lower 121 yen level Wednesday, on expectations that the Bank of Japan and the government may move to stem the unit from plummeting further, triggering a fall in Tokyo stocks. The 225-issue Nikkei Stock Average ended down 225.17 points, or 0.80 percent, from Tuesday at 28,027.25. The broader Topix index of all First Section issues on the Tokyo Stock Exchange finished 24.06 points, or 1.21 percent, lower at 1,967.60. Decliners were led by marine transportation, iron and steel, and oil and coal product issues.