* Nikkei rises 0.9 pct, Topix gains 0.5 pct * Yen weakness boosts exporters, shrugging off weak data * Nikkei up 23.2 pct this year, yen falls 12.4 pct vs dollar By Dominic Lau TOKYO, Dec 28 (Reuters) - Japan's Nikkei average rose to a 21-month high on Friday, heading for its best yearly gain since 2005, as exporters were buoyed by a weaker yen on expectations of aggressive monetary stimulus under new Prime Minister Shinzo Abe. Export-focused firms leading the index higher included Toyota Motor Corp, Honda Motor Co, Canon Inc and Nikon Corp, up between 1.2 and 2.4 percent. Index heavyweight and industrial robot maker Fanuc Corp gained 1.7 percent. The Nikkei advanced 0.9 percent to 10,412.73 in mid-morning of its last trading day of the year, touching its highest level since March 11, 2011 and shrugging off a slump in Japan's factory output in November. "We expect the yen to hit 90, and the Nikkei to reach 11,000 as early as late January or early February," said Shun Maruyama, chief Japan equity strategist at BNP Paribas. "The market is pricing in a new inflation target of 2 percent. However, the problem is how to achieve the target. The market is focusing on what the BOJ will announce in its next meeting." Maruyama said if the Bank of Japan, which is to hold its next policy meeting on Jan. 21-22, fell short of market expectations, investors would take profit. The benchmark Nikkei has rallied 20.2 percent over the past 6-1/2 weeks, on speculation that Abe will pursue policies to weaken the currency, which has hurt Japanese exporters' competitiveness and their overseas earnings when repatriated. The Nikkei is up 23.2 percent this year, on track for its best yearly gain since 2005, while the Japanese currency has lost 12.4 percent against the greenback this year, and is set to post its biggest annual loss since 2005. The yen hit a more than two-year low of 86.64 to the dollar on Friday. The broader Topix index gained 0.5 percent to 858.00. Nippon Electric Glass Co, however, shed 3.5 percent after the glassmaker cut its earning forecast for the nine-month period through December, citing a price decline in glasses used in flat panel displays.