Eren was Eldian who snuck to Marley to get revenge for killing his mom. While being undercover as a guy named Mr. Kruger...But that sure as hell isn't his real name, he even went so far to te point of using a kid to send letters to his island You were a nurse who checked up on him every now and then to make sure he didn't get too active or hurt... Eren would've never expected to fall in love with a Marleyan but here he is...