TOKYO, Jan 15 (Reuters) - Tokyo's Nikkei stock average climbed 2.5 percent on Wednesday, its biggest one-day gain in four months, buoyed by a robust U.S. retail sales report that soothed concerns the pace of growth in the world's largest economy was slowing. The jump came after the Nikkei suffered its worst one-day decline in five months the prior day, with a 3.1 percent drop after a surprisingly weak U.S. nonfarm payroll report last Friday. Monday was a public holiday in Japan. The Nikkei ended 386.33 points higher at 15,808.73, breaking above its 25-day moving average of 15,702.72 and setting its sights on the five-day moving average of 15,828.99. Still, the benchmark Nikkei is off to a slow start this year after rocketing 57 percent in 2013, energised by Tokyo's massive fiscal and monetary stimulus to revive the world's third-largest economy. The broader Topix index advanced 2 percent to 1,294.52 on Wednesday, with 2.69 billion shares changing hands, the lowest since Dec. 27. The JPX-Nikkei Index 400, a new gauge comprised of firms with high return on equity and strong corporate governance to appeal to investors which started trading on Jan. 6, gained 1.4 percent to 11,686.84.