Title says it all. What happens when Castiel's sister starts dating his worst enemy?

Nelly Carter is moving to Sweet Amoris high with an English teacher as a stepdad and low expectations, with no belief in the existence of love. Castiel Mason is hung up on a love that never existed to begin with. Bonding over music and sarcasm, the two quickly become inseparable, but an overwhelming amount of obstacles stand in their way, and there may be too many to overcome.