All the goals came in the second half, with Chikashi Masuda, Han Sang-woon and Kin Shin-wook finding the target.
Suwon Bluewings missed the chance to go clear at the top, going down 2-1 at Busan I'Park.
Kim Dae-kyung put Suwon in front after just four minutes but Lim Sang-hyub (11) and Jang Hack-yong (78) won it for Busan.
Jeonbuk Motors are two points off the summit in third following their 2-0 win over Daegu FC.
Leonardo opened the scoring in the 37th minute before Eninho sealed it on the hour mark.
Seongnam Chunma were 2-1 winners at home to FC Seoul.
Lee Chang-hoon struck the decisive goal after efforts from Kim Dong-sub and Kim Chi-woo cancelled each other out.