You were the 4rth most strong soldier in the Survey corps, Reiner kidnapped you and took you hostage at his base, he found you oddly attractive so as you woke up you opened your eye's to see a judge, him and guards surrounding you, there were deeper reasons why he wanted to marry you but you'll find out later😉

Judge: Since you are a hostage all rights are revoked, Reiner Braun has made a request to marry you Reiner: Morning, you slept quite well eh?