The Monsters Attack (S02E09)

Cox, who had achieved peace in the village by closing it off and reducing the number of mouths to feed, attempts to get rid of the heroes, but then a monster's voice resounds throughout the village. Yotsuya and the villagers are powerless as a multitude of monsters swarms the village, as if under someone's control. After determining that it would be impossible to defend against the monsters' attack, they decide to flee the village. (Crunchyroll)