Lee Keun-Ho scored and set up another goal as Ulsan defeated Kashiwa Reysol 3-2 in the AFC Champions League round of 16.
Wednesday's victory means Ulsan have advanced to the quarter-finals where they will be joined by Guangzhou Evergrande after the Chinese club defeated Tokyo 1-0.
After a scoreless first half, Ulsan sprang into life, with Lee setting up the opener 10 minutes after the break.
The 27-year-old attacker weaved his way through Kashiwa's defence to the right-hand side of the penalty area and then chipped the ball to the top of the six-yard box where Kim Shin-Wook headed home.
Kashiwa equalised in the 68th minute when Leandro Domingues got his head to a long throw to nod the ball into the back of the net but four minutes later Ulsan were in front again when Japanese defender Naoya Kondo poked the ball into his own net.
In the 89th minute, Lee hit a brilliant third goal for Ulsan.
Lee controlled the ball on his chest on the edge of the area, before thumping it past keeper Takanori Sugeno to seemingly seal Ulsan's place in the quarter-finals.
But in stoppage time Kashiwa reignited their chances of forcing exta-time when Junya Tanaka struck a brilliant left-foot shot across his body inside the far post.
Ulsan held on, however, ending Kashiwa's involvement in the ACL.
Guangzhou's 1-0 home win over Tokyo ensured that no J. League clubs will be involved in the ACL quarter-finals.
The Chinese Super League club moved into the last eight for the first time thanks to a 31st-minute goal from Cleo.
Cho Won-Hee cut in from the right wing and laid the ball off to Brazilian forward Muriqui before bursting into the box.
Muriqui expertly chipped Tokyo's defence putting the ball in front of Cho, who centred for Cleo to finish.