These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Awesome Art: There are some very nice lighting and scenery setpieces in the anime's first two episodes alone, centering on the rural landscape around Ai's village. When the characters start their journey, it only gets better, especially the city of Ortus.
Jerkass Woobie: Hampnie. He's not very likable at first, and he uses his cruelty to hide his pain. The love of his life left him without warning, and due to his immortality he's afraid of being the last human being on Earth, and when he finally realizes Ai is his daughter, he can only spend a day with her before being put to rest for good.
Julie. After losing his family, he attacks Hampnie for revenge (or to die at Hampnie's hands). After Hampnie dies, he does calm down, trying to stay strong for Ai and the others, but the loss of his family still affects him, even as he tries to hide his pain.
Scar. She's polite and always smiling, but it's implied she's been through a lot of hardships. And then becomes Not So Stoic when she undergoes an identity crisis.
Ai and Ulla are more traditional woobies. Ai loses her mother at a young age, loses her entire village in a day, and has to bury her own father after knowing him for only a few days. Ulla can kill the living with her voice and eyes alone due to her mother's wish, a fact the city of Ortus tried to keep from her. She is also the only living being in Ortus, and she can only interact with the dead. But she has Kiriko, and she keeps in contact with Ai through letters.
Tanya from Goran Academy. Born blind, she made a wish to be able to perceive shapes and colors as sounds, and then her village started treating her like a freak.