Kira Sakuya
Warning: Some light spoilers (depending on how you see it). o_O; So read with caution, or read the manga before this.
Name: Kira Sakuya
Age: High Teens (Senior year)
English Voice Actor: Vinnie Penna
Japanese Voice Actor: Takehito Koyasu
Also, known as "Senpai" (meaning: elder schoolmate) called by Setsuna, Kira is a high school senior in Tokyo, Japan. He's friends with Kato (Oo; Kira tries to prevent him from being a drug addict) and Yoji and looks out for Setsuna. He kind of portrays himself like a role model that Setsuna and Kato can look up to. In his present state, Kira is admired for his incredible fighting skills. He is also has his way with girls @_@;; (quite flirtatious: "Oh, what's that? You wanna see my room? Come on, let's go.") However, there is a darker past within him...
Kira is the soul of Lucifer (Nanatsusaya- amulet), the lord of the underworld. Lucifer was detained in a sword by the Angels. In the battle between Alexiel and Rosiel, Rosiel's blood got caught on the sword (which you may see a blood stain on Kira' chest, which gave him the power to live on forever). This sword was wielded by Organic Angel- Alexiel, and Lucifer's soul was able to protect her, thus Alexiel easily handled the sword. And soon Lucifer was in love with Alexiel.
The real Kira Sakuya was died at a young age along with his mother. Then, a figure of Lucifer comes up to the young Kira and asks him what would he do if he could live longer. Kira responds that he would read a lot of books and study the world. Lucifer offered a deal with him to use Kira's body to complete his goals and grants the wishes of whatever Kira wants to do. Kira says that eventually he will die again, and wants to make his father (Sakuya-san) hate him so that Sakuya-san won't have to grieve twice for Kira dying. (You see in some scenes where the older Kira is smoking, drinking, womanizing to deflect his father's attention). However, later on, Kira tells Sakuya-san that he is not his real son and that is only a freak, and told him to go back to Hokkiado (to avoid the dangers that were coming). Amazingly, Kira saw that Sakuya-san had come back for him and that he loved Kira no matter what he was and cared for him like a son. Kira was in pain and hurt because he didn't want to be close to anyone, unaware that he had become a human. Young Kira is deep inside in the present Kira, who gave him a heart and emotions like a human to care for Setsuna, Kato, and Sakuya-san contrasting to his callous and cold behavior.