Reqieu Morgan

Always calm, patient, and fair, he's been Iris' capable teacher since she was a child. He cares a lot about her and his other students, and does what he can to help them grow. He specializes as a Purifier instructor but can teach just about every subject.

[spoiler]After his parents were killed during a corrupted spirit invasion, he grew up rough on the streets with his twin sister, Morgen. Living strategically, they were able to achieve a normal living, but Morgen was killed in action over a decade ago. Reqieu has learned to live alone for the most part, but quietly carries the weight of her loss with him.[/spoiler]

[From official bio]