Two Asian teenagers, both 19, have advanced to the second round of the US Open, set to make warnings of a rising young generation of stars come true on tennis' biggest stage. Japanese qualifier Yoshihito Nishioka outlasted France's Paul-Henri Mathieu 6-4, 2-6, 6-7, 6-1, 6-2 after three hours and 22 minutes in sweltering heat while South Korea's Chung Hyeon ripped Australian James Duckworth 6-3, 6-1, 6-2 in 96 minutes.