The Bank of Japan’s restraint is a gift for China. The yen surged 1.7 percent against the yuan as of 4:43 p.m. Shanghai time, the biggest gain since April 28, after the BOJ refrained from easing monetary policy. That’s a tailwind for China after the yuan dropped to its lowest level versus the Japanese currency since October 2013. The yuan’s 14.6 percent decline against the yen this year is aiding Chinese companies that compete with Japanese exporters in overseas markets. China’s outbound shipments climbed for a third month in May in yuan terms, while Japan’s exports have fallen every month since October. Concern over Britain’s vote next week on European Union membership is adding to yen strength as investors pull out of riskier assets to seek havens. The yuan declined toward a five-year low against the dollar after strengthening Wednesday following a Federal Open Market Committee vote to leave interest rates unchanged. “The yen’s rise against the yuan will be favorable for exports as it was tough for China when Japan’s unprecedented monetary easing weakened the yen quite a bit,” said Ayako Sera, a Tokyo-based market strategist at Sumitomo Mitsui Trust Bank Ltd. “If the Fed pushes back its rate hike, the yuan’s depreciation pressure will decrease and, given that it’s a controlled currency, it’s easier for the yuan to weaken against the yen.” The yen’s surge is undermining BOJ Governor Haruhiko Kuroda’s efforts to bolster economic growth. The Japanese currency is the best performer against the yuan in Asia this year. The BOJ held its key interest rate at minus 0.1 percent and kept the annual target for expanding the monetary base at 80 trillion yen ($767 billion). The Chinese currency weakened 0.09 percent against the dollar onshore and 0.04 percent in Hong Kong’s overseas market. The People’s Bank of China strengthened the yuan’s reference rate by 0.4 percent against the greenback. A measure of expected swings in the yuan rose to an 11-week high on Wednesday amid uncertainty over Fed policy and as MSCI Inc. said it wouldn’t include Chinese stocks in its global benchmark indexes. MSCI, whose emerging-market gauge is tracked by investors with $1.5 trillion in assets, cited the need for additional improvements in the accessibility of China’s share market and said that it would reconsider inclusion in 2017. China has taken several steps to support the yuan this year, including selling dollars and getting officials to talk up the currency. Chinese holdings of U.S. stocks sank about 38 percent from the end of July through March, suggesting the PBOC was under pressure to raise dollars and smooth the yuan’s depreciation.