well, they have psychic vector hands, they have instinctive desire to kill humans while intinctively friendly to other animals, so I won't say they are humans. Humans have instinctively cruel to other animals. Judging by the title, they are meant to be something similar to elves I guess. Also Karma is different from social laws and things. Actually now I think about it, if we go by the concept of Karma as in Buddhism, then you indeed need to pay for killing and eating pigs because of Karma
As far as I see, there's no major theme like "forgiveness" or "karma" in this series. You are putting too much emphasis on Lucy, while in the show it has a lot to do with Nana and Mariko and the other characters. Really, it's not that focused on Lucy. So I'd say it's more about beings different from humans in a human society, rather than some personal forgiveness or karma stuff about Lucy. How many episodes out of the 13 has anything even remotely to do with Lucy's "karma"? 2 to 3 episodes at most. that's hardly a main theme or focus.