For Tadashi Yanai, the founder and president of the Uniqlo parent company Fast Retailing, the United States has become a source of both immense optimism and concern.

In recent years, Uniqlo’s affordable, well-made basic clothes have struck a chord, especially with younger American shoppers, fueling a rapid business expansion. The United States is now a pillar of the growth strategy of Japan’s Fast Retailing.

Yanai, 76, came of age in postwar Japan, steeped in American culture. He wore Converse and drew inspiration for Uniqlo from casual-wear brands like Gap. Conquering the U.S. market is also a matter of personal legacy for Yanai, whose Uniqlo empire today comprises more than 2,500 stores globally.