Eren Jaeger's adopted sister is Mikasa Ackerman (Mikasa Wallpaper
Aesthetic). She owes him a great debt because he rescued her from kidnappers
who wanted to sell her as a slave and they spend the majority of their time
together.
So, even if she doesn't always agree with what he does, she
defends him against anyone who tries to harm her. She and Armin join the Scout
Corps to assist Eren in retaking the Mary Wall. She is regarded as a military
prodigy and graduated first in her class in Troop Recruitment Cycle #104.
Check out this wonderful
collection of Mikasa Ackerman wallpapers, which includes 45 Mikasa
Ackerman desktop wallpapers.