This is a manga series about The immortal Methuselah. His real name is Rain. He was part of a scientific experiment a couple centuries ago, and since then has been hunted contstantly. He can be stabbed, hurt, and shot, but will never die, until he again meets the man that made him so.

His companion is the young bounty hunter, Machika. She is out for his head because he is the one that caused the death of her grandfather, the legendary bounter hunter Zol. But she is slowly coming to care for this mysterious loner for who a human life passes in the blink of an eye, and he for her. She wants to help him find peace at last, be it in final death, or a return to humanity. This is a tale of their budding feelings and trials in the search for Rain's destiny.

((This is one of my favorite mangas. I, for one, would write about it if it made it to the list.))