the favor | clexa AU

There isn't much that's worse than no experience when you want to impress someone. Lexa is itching to get Costia's attention and liking and because of her lack of experience in sleeping with people, she asks her best friend and roommate Clarke to help her out.
It's just a favor. Just one time for educational purposes. Just one night that starts a little awkwardly and ends in the struggle of ignoring you fucked the person you live with and that matters to you the most. Of ignoring it might've just been the best night of your life.
But the promise stays. One time and never again.

Right?