http://www.asianfanfics.com/story/view/659609/ludos-highschool-exo-kai-kris-teenlove

Title - ludos

Status - Completed

Her :

Because when your bestfriend betrays you, the only way to get back at her is to make her crush your boyfriend.

Him :

Because when you’re the biggest Casanova in school, the only way to stay as one is to get the targeted junior as your girlfriend.

Them :

If it is not obvious enough, they are starting to fall for each other, hard.