From the start it was pretty obvious that he was a psychopath. He learnt how to fit in, and he used his age to his advantage. The cult was crazy tho, the art was so perfect for this type of story, it perfectly conveyed the fucked up feeling. I liked the ending of this, it wasn't shown as a punishment for him, but rather just a consequence of his actions. It even showed us that the cult was still there, it probably didn't end with his death alone, whether these children in the cult would grow up to be like him or leave this alone as a part of their dark past, we'll never know.
KAMI NO KODOMO