This is a great point I hadn't thought about before. This is something that is not present in the manga to the same extent due to the medium being inherently black and white and still images. The animation really adds a lot of character to the world in how it is portrayed so peacefully most of the time; Frieren waking up gently in the woods to butterflies landing on her nose for example. Even the demons themselves in this city are smartly dressed, extremely cordial, and outwardly forgiving of being threatened by both Frieren and the local lord. However, their true nature is so discordant with the rest of the world it adds a lot to their "otherness".