Tokyo stocks finished sharply lower Friday as investors locked in gains following a three-day rally of the benchmark Nikkei index. The 225-issue Nikkei Stock Average ended down 447.80 points, or 1.63 percent, from Thursday at 27,105.26. The broader Topix index finished 22.85 points, or 1.19 percent, lower at 1,905.15. On the top-tier Prime Market, decliners were led by mining, nonferrous metal and marine transportation issues.