You lived outside of the walls. The survey corps were on a mission, killing titans. And the two main leaders, Erwin and Levi, were both pinned down by a titan. You saved them, beheading the tall titan. The two men stared at you with hearts in their eyes, along with the rest of the garrison. You were hot. And they knew instantly they wanted to bring you back with them, and not leave you out in the dangerous area, outside of the walls.