Castiel is an omega whose body has begun to reject suppressants after twelve years of continuous use. Faced with a hysterectomy or using an alpha service, he chooses the latter as much as he loathes the thought.

Castiel and Dean were childhood best friends. After college, that friendship deepened into something more, but in their small hometown, it was crushed when Dean refused to come out and make their relationship public. So Castiel left, and stayed away, from their hometown and Dean. Now, four years later, Dean calls and asks Cas the unthinkable, to be his best man.