Bruh, why the heck is this an extra episode?! The second half almost made me cry, easily my favorite part of the anime. It didn't really introduce new themes to the main story, but it does show a slightly new perspective to it that makes the whole thing much more impactful to me. I thought the main story is great but slightly undercooked in some areas, this episode made up for it with a very touching ending. I don't think I'll ever see zombies in the same way after this, it does make me feel slightly depressed just thinking about them.