An Angel who did not so much Fall In Love as Settle Into It Gradually (слэш)

Crowley was standing in the middle of the room, hands in his pockets, looking a little lost. Aziraphale eyed the distance between them. Five steps. Five steps, and six thousand years, and a battlefield spanning an eternity.
 
The story of the little moments over the millennia that shape an angel’s regard for a demon, and the way he slowly, with great reluctance but inevitable surety, falls in love.