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

Here is Why You Need An Adapter

The outlet and plug type used in Equatorial Guinea are C and E 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

Equatorial Guinea

In Equatorial Guinea, outlets of type C and E are in use.

Type C

Type E