Tokyo stocks tumbled 2.45 percent Thursday as the market was dragged down by worries over emerging markets, after the Federal Reserve further scaled back its stimulus programme. The benchmark Nikkei-225 index slumped 376.85 points to 15,007.06 -- wiping out its 2.70 percent gain Wednesday. The Topix index of all first-section shares fell 2.55 percent, or 32.09 points, to 1,224.09.