There's a fanfiction called 'Love in the Shadows: Scout x Femle Spy'. This one delves deep into the backstories of both characters. It shows how their different upbringings and experiences in the world of espionage affect their relationship. The author does a great job of building tension and chemistry between the two, and the story has a really engaging narrative that draws you in from the very beginning.
One popular scout x femle spy fanfiction is 'The Unlikely Alliance'. It explores their relationship in a unique way, with exciting action scenes and some really interesting character interactions. Another great one could be 'Scout and the Spy Girl', which focuses more on the emotional side of their relationship as they work together on various missions.