TOKYO, Dec 27 (Reuters) - Japanese shares ended lower on Monday, with SoftBank Group leading losses, as concerns over the impact of the Omicron COVID-19 variant offset gains in heavyweight technology stocks. The Nikkei share average (.N225) slipped 0.37% to close at 28,676.46, while the broader Topix (.TOPX) lost 0.45% to 1,977.90. Global technology investor SoftBank Group (9984.T) fell 2.96% on news that Credit Suisse is seeking information through U.S. courts, which could lead to it taking legal action in Britain against the Japanese company to recover certain funds. read more "We do not have market moving events at home or abroad, and many people are still away from the markets, it is hard to make active bets," said Shigetoshi Kamada, general manager at the research department at Tachibana Securities. The volume of shares traded on the Tokyo Stock Exchange"s main board was 0.78 billion, compared with the average of 1.19 billion in the past 30 days. "Under this environment investors chose to bet on a particular group of stocks, which were heavyweight chip-related, and any other shares were sold for an excuse of fears for the Omicron," Kamada added. Technology shares advanced, with chip-related Tokyo Electron (8035.T) and Advantest rising 2.09% and 0.83%, respectively. Game maker Sony Group (6758.T) gained 0.67% and medical equipment maker Terumo climbed 0.47%. Retailers, meanwhile, took a hit as more cases of the highly transmissible variant were found in Japan, raising concerns of tighter curbs slowing the economic recovery from the pandemic. read more Uniqlo clothing shop operator Fast Retailing (9983.T) was the biggest drag on the Nikkei, falling 1.75%. Home interior goods retailer Nitori Holdings (9843.T) tumbled 6.53% and Muji-brand retail stores Ryohin Keikaku (7453.T) lost 1.59%. There were 50 advancers on the Nikkei index against 169 decliners.