Quini6
(Story translated into English with permission from @KaiserGuillermo)
Based on the character "The Eternal Champion," created by Michael Moorcock.
Y/N, the Eternal Champion, is a hero who exists across every dimension, timeline, and world, chosen by a cosmic force he can't even begin to understand. He is bound to endlessly fight against chaos, order, and the slow decay of the worlds he is forced to enter. Most of the time, he doesn't even know what role he's supposed to play, or worse, he does know and still fights against it, only to never truly win.
The Eternal Champion is constantly surrounded by conflict and destruction. Moments of peace are what he values the most, because that's when he can pretend to be someone normal, when he can almost convince himself that he's human.
Y/N stands in the middle of a wide plain when suddenly a 12-meter humanoid appears. Already irritated from being thrown into yet another world by that same cosmic force, he doesn't hesitate. With a single strike, he tears it apart.
Now he's about to get dragged into the conspiracies of the world of Attack on Titan.
(This story takes place after the fall of Wall Shiganshina, during the training period of the 104th Cadet Corps.)