Fionna was just going on with her everyday routine life, but her perfect little world is turned upside down when Marshall shows up. At first all he does is bother, pester and annoy her. But he slowly creeps up on her and Fionna unexpectedly starts to form feelings for the classic bad boy. And he might feel the same way. But life isn't all sunshine and rainbows is it?

Setting AU High school; Fionna and Marshall Lee have always been enemies since they could remember. Ever since Marshall had bullied her best friend, Bubba Gumball, at the playground, they can't stand each other. And everyone knows it. He was a bully. She, the school hero. Like oil and water, they were not meant to mix… Rated T for now, but might change in the future. Not sure.