Tokyo's benchmark Nikkei stock index soared more than seven percent on Tuesday, boosted by a weak yen and aggressive asset-buying from the Bank of Japan. The Nikkei 225 index rose 7.13 percent, or 1,204.57 points, to close at 18,092.35, while the broader Topix index was up 3.18 percent, or 41.09 points, at 1,333.10. si/ric/amj