Setsuna Mudou is a freshman in high school, who's usually cheerful, out-going, but very short-tempered. He genuinely loves his sister Sara in a way that a brother should not. His body is the reincarnation of the Organic Angel Alexiel, which gives him the gift to see visions and hallucinations. His mother tries hard to keep him and Sara away from each other, and his father (who he lives with) is a very uncaring man. Not only does he have problems with his family, but he has people chasing after him to awaken the angel inside of him. He runs away with Sara so that they can be happy, but later comes back only to have Sara killed and his powers unleashed, destroying the world.
Sara is Setsuna's sister, who also loves him. She lives with her mother, who keeps her away from Setsuna as much as possible (they only visit each other once a month). Inside of Sara is the soul of Jibrille / Gabriel, who was placed in a coma by Sevotharte. When Sara dies, her soul is placed inside of Jibrille's body until Raphael revives her own body.