What is Ellen for Mikasa ? I think he's parent-like someone who's always on her side. What she really loved was Ellen's scarf as her symbol of her father complex. Ellen (=Red Scarf=security scarf=Daddy Ackerman= Defensive lucky charm) in psychology is a complex-a group of unconscious associations, or affection-which ideal lover, family or archetype of the father. These impulses may be either positive (admiring unconsciously and seeking out her father figures) or negative (fear of losing family). So, I think her answer to Ellen's question was right. He was truly her symbol of "family".