First let me say this is better than Attack on Titian. That anime went from horror/gore porn in the first two episodes to standard Shonen anime. Kabaneri of the Iron Fortress also has its flaws but overall I think it’s much better. Don’t take my word for it. Judge for yourself. Even if you disagree with me, the anime is still very good.
The best way I can describe this anime is Resident Evil meets the apocalypse. Humans have almost been wiped out by hordes of zombies. It’s a very serious anime with lots of action scenes. I highly recommend it so stop reading and start watching.