Armistice
With the nation struggling to keep humanity on its last legs, you sneak away to join the military in hopes of bettering its chances of success in the war against the Titans. Your father, however, is displeased with your decision, and he flexes his political power as an esteemed lord and nobleman in an attempt to bring you back home.
You want nothing to do with him, of course, but your freedom from familial ties also depends on how keen command is on keeping you in the Scout Regiment.
You start by building bonds with Levi -- initially, he seems to loathe the fact that you're a member of the aristocracy. When things take turn for the worse with your abusive father, however, he proves reliable, while Erwin proposes a strategy, insane as it is, that you can't refuse.
[Reader x Levi] is the ultimate pairing, but there will be a significant [Reader x Erwin] detour, a love triangle of sorts. Your heart bleeds for both Erwin and Levi, as they discover themselves, brothers in arms, falling for the same woman.