After Everything is the fifth installment in the After franchise, but it breaks away from the rest of the franchise as there is no After Everything book it is based on. The franchise originally launched with the film After, which stars Hero Fiennes Tiffin as Hardin Scott and Josephine Langford as Tessa Young, and the story follows the young couple's tumultuous love story. After Everything was advertised as the final chapter, but it is actually an original story and not based on any of author Anna Todd's novels.
https://screenrant.com/after-everything-based-book-movie-series/