Defrosting Nightfall (Fiona Frost x Male Reader)

You are Y/N, Codename: Sundown. You've only been in the Westalian Intelligence for a few years, but your social skills and ability to adapt have caused you to become a good spy. Twilight is assigned to monitor an Ostanian political party member, and his protégé, Nightfall, returns from a mission. Knowing of Nightfall's obsession with Twilight, your handler assigns both of you to pose as a couple and attend a gala that will be hosted by the Elites of Ostania in a few months. Nightfall's ability to show no emotion and her obsession with her mentor will cause some complications with your "Relationship". But as things progress, you begin to see small signs of things being more than an act.