The Observer

Never forget. Interaction is strictly forbidden. 
They are only human.
Gabriel is an Observer, a member of an ancient race that created
Earth and humanity. His task is simple. He observes humans and reports any sign of interference from The Fallen, people of his kind who have broken their most important rule: never interact with humans. But when Gabriel becomes fascinated with a human girl, Alyssa, it isn't long before he justifies breaking the rule himself.
His forbidden association with her doesn't go unnoticed. The Fallen
seek to recruit him and The Enforcers, a separate caste of his society
who ensure punishment of those who break the rules, force him to
hide--all the while trying to combat a centuries-old plot by The
Fallen to destroy humanity and claim Earth for themselves.

Spending most of his time on Earth, Gabriel realizes he's acting more like a human than an Observer, and he must make a choice: sever all ties with his people, or lose the woman he loves.