You Do Need power plug adapter while traveling from Hong Kong to Eritrea.

Here is Why You Need An Adapter

The outlet and plug type used in Eritrea are C and L and in Hong Kong is G. This is how they look like.

Hong Kong

In Hong Kong, outlets of type G are in use.

Type G

Eritrea

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

Type C

Type L