Tokyo shares opened slightly lower on Monday as market players here tended to lock in recent gains after Nikkei's four-day uptrend. At 9: 15 a.m., the 225-issue Nikkei Stock Average lost 23.23 points, or 0.15 percent, from Friday to 15,250.84. The broader Topix index of all First Section issues on the Tokyo Stock Exchange was down 3.53 points, or 0.29 percent, at 1, 233.44.