Tokyo stocks dropped sharply Friday morning, with the key Nikkei index briefly sliding over 2 percent, weighed down by overnight losses on Wall Street as investors locked in gains after recent rapid advances. The 225-issue Nikkei Stock Average fell 847.29 points, or 1.65 percent, from Thursday to 50,434.54. The broader Topix index was down 27.59 points, or 0.82 percent, at 3,354.13.