* More firms cut forecasts, adding to growth concerns * Nikkei down 0.1 pct; Topix slips 0.2 pct * Softbank up on eAccess purchase, rival KDDI down * Firms' share buybacks down 26.2 pct in April-Sept yr-on-yr -Nomura By Dominic Lau TOKYO, Oct 2 (Reuters) - Japan's Nikkei slipped on Tuesday on concerns over company earnings after a handful of firms cut forecasts, but losses were capped by gains in mobile operator Softbank Corp after its purchase of a smaller rival. The Nikkei eased 0.1 percent to 8,786.05, hitting a three-week closing low for a second day in a row. "It's going to be shockingly difficult earnings season to trade ... downward revisions are going to come in thick and fast and people are rapidly pricing them in," a senior trader at a foreign bank said. Clothing store chain Shimamura Co Ltd sank 4.1 percent after reporting a 3.9 percent drop in second-quarter earnings ended Aug. 20 compared with a year earlier, due to higher costs. Electronic parts maker Alps Electric Co Ltd, which slumped 12.4 percent, slashed its operating forecast by 46 percent, while shipper Mitsui O.S.K. Lines revised its first-half forecast to an operating loss of 3.5 billion yen ($44.84 million) from a previous estimate of 1 billion yen profit. The announcements followed cuts in guidance from steelmaker Daido Steel, shipper Nippon Yusen KK and electric insulator maker NGK Insulators Ltd. The latest quarterly earnings season will kick into high gear in the next three weeks. Investors were disappointed with the previous quarterly earnings, when 54 percent of Nikkei companies reported results below analysts' expectations. For this quarterly results, SmartEstimates from Thomson Reuters StarMine expects an average negative earnings surprise of 1.2 percent. Mitsui O.S.K. surged 4.5 percent as traders said investors had been expecting sluggish earnings from shipping companies due to slowing global growth, while campaigns for higher freight rates from other shippers also aided the stock, which had lost 40 percent on the year as of Monday. "We are expecting bad news for exporters and cyclicals and quite strong performance from domestically oriented stocks, so unless the latter dazzle they're not going to gain," Hirokazu Fujiki, manager of investment strategy at Okasan Securities. SOFTBANK UPS THE ANTE Index heavyweight Softbank climbed 2.9 percent after it said it would acquire smaller rival eAccess Ltd in a $1.84 billion deal to improve its high-speed data frequency spectrum and its competitiveness against KDDI Corp. KDDI and Softbank are the only mobile carriers in Japan to offer Apple Inc's iPhone, including the iPhone 5. KDDI lost 2.3 percent, while eAccess jumped 21.1 percent to 23,000 yen but was still way below the 52,000 yen per share that Softbank will pay for every eAccess share under a share swap deal. The broader Topix index fell 0.2 percent to 731.19 in light volume, with nearly 1.36 billion shares changing hands, down from Monday's 1.38 billion and last week's average of 1.6 billion. Nomura Securities said the uncertain global economic outlook might have led to Japanese firms cutting back their share buybacks in April-September, the first half of Japan's fiscal year, to 509.8 billion yen, down 26.2 percent from 690.8 billion yen for the same period last year. But it expected Japanese firms to step up buybacks in the second half of this fiscal year ending March 2013. "If H2 buybacks were to increase less than expected and fall well short of the FY2011 figure (1.63 trillion yen), however, investors may no longer feel that Japanese companies are proactive on shareholder returns and their interest in the Japanese equity market and listed companies could wane further," it said in a report. The Nikkei has risen 3.9 percent this year, trailing a 14.9 percent rise in the U.S. S&P 500 and an 11.4 percent gain in the pan-European STOXX Europe 600. Still, Japanese equities are slightly more expensive than their European peers but cheaper than their U.S. counterparts. According to Thomson Reuters Datastream, Japanese stocks carry a 12-month forward price-to-earnings ratio of 11.6, versus the STOXX Europe 600's 11.1 and the S&P 500's 13.1.