Nikkei opened 0.70 percent lower Friday. In the first 15 minutes of trading, the 225-issue Nikkei Stock Average lost 62.58 points, or 0.70 percent, from Thursday to 8,921. 20. The broader Topix index of all First Section issues on the Tokyo Stock Exchange dropped 4.61 points, or 0.62 percent, to 739. 18.