The Hidden City

I don't have a solid plan for this book, so this will probably change. I'm sorry it's a little ramble-y. Thank you for cheking out my story :)
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Ria Pearson is normal, or as normal as an antisocial highschooler can get. Bullies, best friends, and feelings aren't even the worst of her troubles, though, when she discovers that one of her classmates is a demon.
Koal, or Prince Koal'Ren as he is known in the city of Ardylet, is in the middle of fighting a man from another world when she happens upon them. Since she has seen them fighting in their true forms, Koal is forced to bring her back to Ardylet with him.
On the other side, Cassiel is the smartest man in Ardylet, and the cruelest. When she appears with Koal in Ardylet, he argues for her interrogation then execution, but is overthrown by Koal. He then watches Ria while she is paraded at Koal's side. Eventually, he discovers that Ria is much like him and coldly analytical. Her curiosity in his lab leads them to fight over and over again, until finally he relents and they grow closer and closer.
Unfortunately, good things can't last forever. Another world with access to the Human World has become infuriated with Ardylet's claim on the world and exacts their revenge in any way they can. As Ria finds herself in the line of fire and torn between two men, all she wants to do is go home. But can she ever return to a normal life after what she's discovered?