You're Mikasa

After seeing a Titan kick a huge hole in the wall, you and Eren rush to your house after Armin scurried away to his grandpa. As you approach, you see Eren's mom trapped under the roof. She reassures you two to leave her, as her legs don't work. You both run away. Eren calls for you

"Mikasa! There's a titan behind us!"

You look back and see a Titan. You carry Eren on your shoulder, then change directions. You manage to get away and through the gate of the wall.