Reito is the vice president of the Fuka Academy student council. He is quite popular with the female students and is interested in Mai.
It is eventually revealed that he is the host of the Obsidian Lord, the main villain of the series. Nagi also divulges that he is actually Reito Minagi, the missing elder brother of Mikoto. Using this fact as leverage, the Obsidian Lord controls Reito into making Mikoto fight the other HiMEs, but he is eventually defeated and Reito is freed of the possession.
