You Do Need power plug adapter while traveling from South Africa to South Korea.

Here is Why You Need An Adapter

The outlet and plug type used in South Korea is F and in South Africa are C, M and N. This is how they look like.

South Africa

In South Africa, outlets of type C, M and N are in use.

Type C

Type M

Type N

South Korea

In South Korea, outlets of type F are in use.

Type F