Raphael

Raphael is an angel whose foremost physical feature is a singular wing. He is a professor at the Angel School with Mikael as his student. He cannot be seen by most of the human world, with Noelle, Mikael, and Natsumi as exceptions and only Mikael can touch him. However, he does influence certain events of the series, in particular rescuing Noelle, Yuusuke, and child Natsumi when he grants Noelle the temporary power of flight as they fall from the clock tower in episode 13. He is benevolent and willing to assist Mikael and Noelle in their quest to become angels, and he has a romantic relationship with Mikael.

(Source: Wikipedia)