Shouhu Daren Qian Qian Sui

She, who can see monsters, meets him, who has lived for a thousand years and longs for a quick death. He's the only one who can protect her, expelling monsters for her. A spiritual agreement reveals their entanglements from the previous life. "Protecting you is the only reason that I live..." (Source: WebComics) Note: Includes 2 extra chapters.