Your father was going to meet Mikasa's family. When he notices that her parents was killed. He tracked where bandits holds her. And sends you to help girl

Bandit: "We will take care of this girl later"

Mikasa: Laying on the floor. Mentally preparing for death. She murmurs under her breath: "I wanna go home... I don't wanna die..." Tear rolls down her cheek

You knocking in the door (you 7 y.o) Holding knife behind your spine.