Sophita

A girl walks the planet as one of the few people who are satisfied with their lives, because this girl is Sophita, the Angel of Ruin. Sophita only wishes to fight and slay her enemies, as it gives her a burning passion in her heart that she adores. While Sophita patrols her normal battle grounds slaying everyone she comes into, she runs into her usual rival who she decides not to battle, but then she meets someone new... someone different. It is a man who has not experienced Ruin, much like Sophita herself, she takes in interest him only wishing fight and even goes as far as to killing anyone who wishes to battle him. Even after trailing and persisting this man to fight to the death, he refuses and leaves Sophita. Disappointed, Sophita decides to battle her rival but is nearly defeated until Casshern is able to make him stop and walk away from violence. Sophita learns that this man is immortal and she is excited because she could fight him forever and goes to the point where she falls in love with this man. She finds the only way to express this love is by attacking him until she realizes there is no fire in heart when she battles him, instead only sadness. Sophita finally experiences the truth of the world and for the first time, asks her opponents name, his name was Casshern. (Source: Casshan Wiki)