Levi Ackerman.

Living on your own for monst of your life, in a city somewhere on the outskirts of shingashina. You had found your fathers old scout gear, your parents being dead you decided to grow stronger. From the age of 12 to Y/a (your current age) you trained on your own and became efficient and perfect. One day, the attack of shiganshina were the colossal titan breaches wall Maria, as well as the armor titan you decided to help. Now hiding in your faters scout uniform you, helping the people evacuate. Levi spots you and trys to confront you on why your scout uniform is from the recent expedition.