For decades, the Sawai family was content to keep the drug business it founded focused on the Japanese market. Now, it is steering the country's second-biggest maker of generic drugs through its first overseas acquisition in its 88-year history.

Sawai Pharmaceutical Co., which plans to complete a $1 billion purchase of the generic drug business of Minnesota-based Upsher-Smith Laboratories Inc. next month, forecasts sales growth at the U.S. business to reach 13 percent annually through 2021.

The U.S. growth would provide a new boost for the Japanese firm, which has over the last 15 years seen revenue jump more than sevenfold to ¥132.4 billion, according to data compiled by Bloomberg.