Dean and Cas go on a hunt, but will it lead to more?

THIS IS NOT MY BOOK!!! I HAVE NOTHING TO DO WITH THIS BOOK!!!! The original book Twist and Shout by the author from achiveofourown (Gabriel (AO3)) ALL THE CREDITS GOES TO GABRIEL AND STANDBYME!!

Castiel is an Angel of the lord but when his brother Gabriel is called away on a mission of heaven, Castiel is forced to be normal. This involves going to school where he meets the dashing Dean Winchester.

Dean and Cas have been dating for a while now, secretly, but what will happen when Cas' mom and Dean's dad gets married and they become stepbrothers?