Cha Jun-hwan, You Young lead after short programs at South Korean nationals
Toronto-based Cha and Youth Olympic champion You lead despite slight errors in Uijeongbu.
Brian Orser-trained Cha holds a lead of some 11 points over his nearest challenger Lee Si-hyeong, having been the only man to attempt – and land – a quadruple jump.
The Toronto-based skater opened with a quad Salchow, and although he was marked down on his triple Axel, no one else came close.
Cha's score of 90.36 seems unlikely to be challenged by any of the other eight skaters in Friday's free program, as he seeks a fifth consecutive Korean national title.
Meanwhile, Lausanne 2020 Youth Olympic champion You is locked in a tight battle, with just over four points separating her from sixth-placed Wi Seo Yeong.
You was hampered by an under-rotated triple Axel, while her triple flip, triple toe loop combination was called for a quarter under-rotation on the toe loop.
Her score of 69.87 was just 0.65 points ahead of Lee Hae-in, who might have done enough to outscore You if not for an unclear edge on her triple flip.
Kim Ye-lim, who sits third exactly one point behind You, was also pinged by the judges for the same edge error on the triple flip.
The free skates will take place in the reverse order of the short program placings, with Cha and You skating last on Friday.