The only things living on Earth now are zombies and giant monsters some of the monsters are sentient though and to understand human language but none of the monsters have actually seen a human before the only human seen are zombies some of the monsters act like dogs in a way there is one evil monster though that needs a human to open a gate to it out in evil monster that will destroy the world they will also manipulate to gain their trust act like a friend at the end will show there true colors.