“Truth Slash Fiction” is an irreverent dramedy that follows 16-year-old Emma Jacobs as she navigates the indignities of adolescence. Through it all, Emma clings tightly to the songs of the boyband “Truth”: a One Direction-style supergroup whose romantic earnestness is Emma’s only refuge from the often cruel and anxiety-filled social interactions that make up her world. Emma’s love of those sultry-voiced boys leads her to join a group of like-minded fans who channel their devotion in an unusual way: they write slash fiction involving the band they love so much.