Titan killer (Levi X reader)

What if I told you that there was a new kind of powered being? What if you weren't a Titan shifter but a what they call a witch? Well, you're a new kind of Cadet and that did catch a little someone's attention....

You are a part of the military and you are one of the individuals humans fear.

Eren Jeager, Mikasa Ackerman, Armin Arlert and you were best friends since you were kids. You all dreamed of getting outside of the world someday. But something happened... The colossal Titan broke through wall Maria and Titans filled the town. Your house was destroyed by the titans but you somehow managed to survive. Not like your brothers and sisters.... Your parents though we're on a trip to wall rose so they were fine. Lucky you. Even if they refused you decided to join the scouts. And here you are with Eren, Mikasa and Armin, in the training camp. But what happens when the Titans get to wall Rose and you use your ability... What will happen when a little someone turns into a Titan?