An outsider observes changes in Erwin before he became the commander, once he had, and once he'd met Levi. Levi is slightly out of character, but since he's always shown with Erwin - and I imagine he might be softer around him - I bought it.
soooo levi gets injured and erwin takes care of him. also most of the story is from erwins friend's perspective. it mostly focused on erwin as a person and how he has changed over the years of seeing all his comrades die~