Korea grabbed an early lead when Kim Yun-Mi pounced on poor defending from the South Africans in the seventh minute.
Banyana attempted a come back, but a move involving Linda Motlhalo and Thembi Kgatlana failed to bear fruit moments later.
The Asian nation doubled their advantage through Ri Hyang-Sim from lackluster defending once again after 13 minutes.
Yun-Mi made it three shortly after the halfway stage in the first half following an assist from Ri PomHyang.
Ten minutes to halftime, Wi Jong-Sim rubbed further salt in Banyana’s wounds with a good finish from close range.
Desiree Ellis made a double switch at the start of the second half when Kholosa Biyana and Jermaine Seoposenwe came in for Nompumelelo Nyandeni and Karabo Dhlamini.
Banyana give their dire situation a lifeline when Lebohang Ramalepe conjured up an impressive strike two minutes from resumption.
The South African side were buoyant at this stage and seemed to have shrugged off the disjointed first half display, although they still lacked a killer instinct in front of goal.
Whilst chasing the contest, Banyana introduced another change when Kgatlana made way for Amanda Mthandi, as Kylie Swart denied the Koreans a fifth from a free-kick moments later.
Nevertheless, Banyana suffer their first defeat at the tournament, as focus shifts to Czech Republic on Monday.