 Some of Eren 's friends are also revealed to be able to transform into Titans and had been sent as spies by an unknown party to find something called " The Coordinate " . It is later confirmed that the Coordinate is the power to control other Titans at will , and that Eren holds that power . The royal family and the Military Police track Eren and his friend Krista Lenz , who is actually Historia Reiss , the successor to the real king , Rod Reiss , as the current king is but a figurehead . 
