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

Here is Why You Need An Adapter

The outlet and plug type used in Namibia are D and M and in South Korea is F. This is how they look like.

South Korea

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

Type F

Namibia

In Namibia, outlets of type D and M are in use.

Type D

Type M