is this original idea or no? 10 points for non harsh best answers FAST ANSWERS PLZ?

Asked: is this original idea or no? 10 points for non harsh best answers FAST ANSWERS PLZ?

So I'm looking for a way to put my foot into this story idea and make it original without coping some other author. Please let me know and excuse any bad spelling thanks.

There is this angel who was the guardian of the white gates until he was accused of plotting to assassinate the archangel Michael to claim his powers. He doesn't know why this happened but they stripped him of his wings and is losing his powers slowly. The punishment was sentenced to death but was given a year to prove his innocence to Michael by discovering the real killer and destroying the prophecy made in the beginning of time. The prophecy stated that "The Lucifer Three were born to control the three worlds, heaven, earth/limbo and hell. But the demon born human with the mark on her body will destroy the gatekeeper and burn the gates of heaven down to start the distribution of power." Cast out of heaven and now down on earth he realizes he is an open target for the all demons on the Earth already and especially the one meant to kill him.

There is this girl who protects him from a demon capturing who says she hunts them and kills them in order to protect humanity. She has her own psychic powers of her own since Lucifer (will change the name) killed her mother and was abandoned by her father. He starts to feel romantically towards her but she says it can not be since she will help him get his wings back. Later on after a fight has injured her severely, the angel figures out that she is the demon sent to kill him. After learning why she won't kill him and that she will do anything to get his wings back he decides to let her help but doesn't trust her.

The Lucifer Three
The oldest is a son named Brendan
The middle child is a daughter unknown
The youngest is a son names Throne

This is what i got so far please comment on what you think and if this hasn't been used before. And if you have a name for the angel and the girl it will be much appreciated. The best and nonharsh answer will receive the ten points. Thanks alot.