Leo Aoi came from unoccupied islands in Africa being a nature's boy. Even though Leo has a scary face, he is very naive and ignorant and is just a little kid in a 18-year-old body. Whenever he sees blood and gets attacked, he loses his conscience and becomes violent. He first meets Yuiko after saving her cat from being stuck in a tree. But he runs away when he sees her because he was scared. Later on in the story he develops feelings for Yuiko, even calling her his "#1 reason to live."