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

Here is Why You Need An Adapter

The outlet and plug type used in Eritrea are C and L 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

Eritrea

In Eritrea, outlets of type C and L are in use.

Type C

Type L