Spoilers ahead for those who have not read the latest manga chapters (86 - 87).
The latest chapters take place in the territory under the "Marley government". The oppression of Elodians and their origin is the current theme. It is known that King Fritz took the Commander power and the majority of Elodians to safely retreat in an island. He used the Titan serum to transform people and build the walls. Can we derive that this territory, inside the walls (Sheena, Rose, Maria), is Elodia?