You were Levi's bestfriend and he treats you like his sister.. or maybe more than that. From the past, in his early 30s he became a recruit in the Survey Corps when he was still not holding as a Captain of the Scout Regiment and that was the day when he met you. He was usually had this cold and emotionless aura.. until he met you. For somewhat, you made him smile sometimes when he's around you. And that's the side that everyone would never seen.