Nagi Uesugi

Nagi is Kai's "Only friend" and may be in a relationship with Kai. He appears near the end of the 1st episode. He vows to protect Kai from anyone who hurts him, He hates Shou for hurting Kai. In episode 2 he is apparently "killed" to protect Kai from his own attack when he is controlled by Ran. Nagi was awakened as a black-winged in episode 2.

(from Wikipedia)