This man is seen in Rain's flashbacks. His place and purpose is explained throughout the series. His main goal is to end human life as each time he dies he is reincarnated as another human being. Yuca is the reincarnation of the spirit of Methuselah, the name later applied to Rain. He wants to die eternally but the only way to guarantee his final death seems to be having no population left to birthe him. He reincarnates as Ishmael's son (his mother, who is Sharem's sister, immediately dies after giving birth to a child that is already in the form of a young boy), and Sharem names him "Ys" as she believes that he is the reincarnation of her son Ys. He has had experience creating "angels" in his previous "life" so during his life as Ys he creates numerous "angels" as devices for mass destruction. He was the person responsible for Freya's death and production of the biological weapons, and for Rain's immortality. He wants Rain to experience his pain and see his depression from being the person that he is. In a later volume, it is hinted that a part of Yuca secretly wants Rain to stop him.