Understanding the hojuk trick

The agency hojuk trick is to take a Korean child without any birth registration and make a hojuk as if the child has no parents. 

Children that have been registered by Korean family and are registered on the family registration gets a new hojuk by request of the adoption agency.

That means that the child in some cases appears to have two family registrations: One of the Korean family and another "orphan hojuk" produced by the adoption agency. 

The "orphanized" version of the adoptee is the one who is adopted. The real Korean family registered verion of the Korean child "stays" in Korea and is registered still as a Korean citizen in some cases. 

The only official document that the adoptee has is the orphan hojuk and this document isolates the adoptee from the Korean society in a dead end loop made by the adoption agencies.