Rakuten, Amazon’s main rival in Japan, said it will raise 242 billion yen ($2.2 billion) by selling its shares to Chinese internet giant Tencent and U.S. retailer Walmart as well as Japan Post, a postal and financial services group. Japan, the world’s third-largest economy after the U.S. and China, is one of Amazon’s biggest international markets. Rakuten, which operates the country’s largest...