Often, they make up. They realize that their friendship or relationship is more important than whatever they were fighting about. It could be a simple apology scene where they admit their faults and hug it out.
One possible reason could be a misunderstanding. Maybe there was a miscommunication about their career plans. For example, if one of them got a solo opportunity but the other thought it was a betrayal of their duo concept. Another reason might be jealousy. If one was getting more attention from fans or the media, it could lead to tension and ultimately a fight.
Love is also a prevalent theme. Whether it's a slow - burn romance or a love - at - first - sight kind of situation, fanfics love to play with the idea of Louis and Harry falling in love. It can be really sweet and endearing to read about their romantic encounters.
Another theme is self - discovery. The characters of Harry and Louis are often on a journey of self - discovery in relation to their feelings for each other. In some fanfics, they have to figure out who they are and what they really want in terms of their relationship.
Some 'Harry Louis fanfic' stories focus on their growth as individuals. Maybe Harry is going through a tough time in his career and Louis is there to support him. It could show how their bond helps them both become better people. There are also fics that delve into their shared hobbies and interests, like music, and how that brings them closer together.
One common theme is miscommunication. Often in these fanfics, Harry and Louis fight because they haven't been able to clearly convey their feelings or intentions to each other.
One great fanfic is 'Invisible String'. It beautifully weaves a story of their friendship evolving into something more. The writer does an amazing job of capturing the essence of their relationship in the fanfic.