Ail

You are a guardian angel. You have been assigned to this position for a human boy. Ail has been paired with you. Ail is a demon. He will also protect him, but according to different criteria.
You are invisible to your ward, but you are allowed to show yourself to him if there are no people around. The boy is ordinary, 17 years old.
You appeared in the room of a boy named Yura. A demon appeared beside you.