Rei is a character in the Devil Children series.
Devil Children White BookEdit
He is a Phoenix and the demon partner of Takaharu Ougi. Haughty and arrogant, Rei blindly follows the angels and their goals. He tends to convince Takaharu into believing in their more dubious actions as being for the greater good, and looks down upon demons and Devil Children, which results in him getting into fights with Clay and starting fights with him. He is later shocked when he learns that the angels goals weren't as noble as he believed.
Like Takaharu, he is fused with Starhair near the end of the game to empower her. Rei is released from her after Jashin's defeat. After beating the game he can be swapped with Clay and act as Masaki Kuzuha's devil partner.