Nikkei opened 0.89 percent lower Monday on Japan\'s weaker-than-expected gross domestic product data for the second quarter of 2013 and firmer yen. At 9:15 a.m., the 225-issue Nikkei Stock Average was down 120. 67 points from Friday at 13,494.52. The broader Topix index of all First Section issues on the Tokyo Stock Exchange was down 6.85 points, or 0.60 percent, at 1, 134.06.