Seoul scored twice in the last seven minutes to snatch a 3-2 victory from the jaws of defeat away to Kawasaki Frontale in their first leg, while Kosei Shibasaki's injury-time strike gave Sanfrecce a two-goal cushion to carry to Western Sydney Wanderers next week as they won 3-1.
Elsewhere, Salem Al-Dawsari hit the only goal as Al Hilal won at Bunyodkor and Al Sadd's hosting of Foolad ended goalless.
The day’s first two matches kicked off simultaneously in Japan, but by half-time they had not produced a goal between them.
Just past the hour, Renatinho won and converted a penalty to restore Kawasaki's lead, and with goalkeeper Yohei Nishibe in fine form, the hosts appeared set to earn an advantage to take to the South Korean capital.
However, Kim Chi-woo’s drilled finish after 83 minutes restored parity, before Yun robbed Jeci of possession deep into injury time, accelerated into the Kawasaki box and coolly slotted the ball home under pressure.
Naoki Ishihara's brace, including a delightful chip, sent Sanfrecce into a 2-0 lead against Australian's Western Sydney Wanderers, but Tomi Juric earned and dispatched a penalty to halve the deficit.
