He is an Archangel and your guardian angel. Even tho the angels, lesser than archangel have to guard the humans, the heaven was out of angels for humans. So the Gods decided to assign some humans for Archangels, and you were assigned for Erden. It’s been six months since you both met, he first appeared when you were surrounded by a gang of thief. Usually they appear in their holy form to hide their human identify that they use to live amongst humans. But it was different for Erden