Mizuho Financial Group said Friday that it suffered a 36 percent drop in net profit in the first quarter to June, as Japan\'s megabanks reported mixed earnings for the April-June period. Sumitomo Mitsui Financial Group Inc. also reported Friday its net profit in the quarter fell 2.4 percent on year, hurt by higher tax-related costs. Nomura Holdings, Japan\'s largest securities firm, and Mitsubishi UFJ Financial Group Inc. (MUFG), Japan\'s largest bank by assets, reported profits in the period. Mizuho\'s profit slump was due to a falloff in profitability at its banking units, it said, posting a group net profit of 96.4 billion yen ($1.24 billion) for the first quarter from April to June, down 35.6 percent from last year\'s 149.8 billion yen. Mizuho had a computer system breakdown in March that led to disruptions at automatic teller machines as well as salary payments and other transactions that affected millions of customers across the country. Net revenue slipped 11.2 percent to 632.9 billion yen from 713.2 billion a year ago. The bank left unchanged its forecast net profit of 460 billion yen for the year to March 2012. Sumitomo Mitsui Financial Group Inc said net profit fell 2.4 percent in the April-June quarter to 206.6 billion yen. Group operating revenue for the period climbed 19.7 percent from a year earlier to 1.04 trillion yen. The bank left its earnings unchanged. MUFG said its net profit in the quarter tripled to 500.58 billion yen from a year earlier, boosted by a one-time gain from share conversion. In June, MUFG changed its stake in Morgan Stanley from preferred shares to common shares, with its partnership now at 22.4 percent of the voting rights in the US giant. Mitsubishi UFJ owns the chunk of Morgan Stanley after throwing a nine-billion-dollar lifeline to the troubled Wall Street giant in 2008 during the financial crisis. Nomura Holdings Inc. said first quarter net profit grew more than seven-fold on a one-time gain, but unstable market conditions continued to foil its attempt to expand its overseas investment banking operations. Japan\'s largest securities business group by revenue posted a 17.8 billion yen net profit in the quarter, compared with 2.3 billion yen from a year earlier. The better-than-expected profit was driven by a one-time gain from turning Nomura Land and Building Co. into a fully-owned subsidiary as well as strong domestic sales of investment trusts. \"Our wholesale businesses faced a very challenging quarter as markets remained highly volatile, severely impacted by the sovereign crisis in Europe and the earthquake in Japan,\" Nomura chief executive Kenichi Watanabe said. Nomura\'s overseas operations remained in the red as the European, Asian and Oceanic regions struggled. Its group revenue for the quarter jumped 36 percent to 427.0 billion yen from 314.0 billion yen.