Longtime yen bear Nomura Holdings Inc. has finally bowed to the market forces that drove the currency to ¥99 per dollar for the first time since 2011.

It is far from alone. HSBC Holdings PLC, Citigroup Inc., and Mizuho Financial Group Inc. join Japan's biggest brokerage in raising year-end yen forecasts by as much as 20 percent after the U.K.'s decision to leave the European Union spurred a rush for the currency as a haven.

The median of estimates compiled by Bloomberg shifted 3.6 percent stronger in June, the most for year-end forecasts within any year since 2011, when the yen was on its way to a record high following the devastating earthquake and tsunami in March.