TOKYO, Feb 24 (Reuters) - Japan's Nikkei average eased from a three-week high in an erratic session on Monday as a firmer yen and weak Asian markets triggered profit-taking following recent sharp gains. Many investors stayed on the sidelines looking for clearer signs of improvement in Japanese corporate earnings, giving no more than a passing nod to the Group of 20's latest commitment to spur faster global growth. The benchmark Nikkei closed down 0.2 percent at 14,837.68, after surging 2.9 percent on Friday. The Nikkei on Monday advanced as much as 0.8 percent to 14,982.53, its highest level since Jan. 31, and fell as much as 1.4 percent to 14,658.14 during the course of trade. The broader Topix index fell 0.3 percent to 1,219.07, with 2.32 billion shares changing hands, among the lowest volume so far this year. The JPX-Nikkei Index 400, an index launched this year comprised of firms with high return on equity and strong corporate governance, dropped 0.3 percent to 11,030.48.