In the fanfiction, they could have had an argument about a girl they both liked in the industry. This led to a rift between them. However, the girl gets into a difficult situation in her career, and they both realize that their feud is petty compared to helping her. So they come together, put their differences aside, and use their influence to support her. Through this process, they see that they are more alike than they thought and finally make up.
One possible plot could be that they had a big misunderstanding during a music competition. 2PM thought Jay Park was being too self - centered, and Jay Park felt that 2PM was excluding him. But then, they are forced to work together on a special project for a charity concert. As they start rehearsing, they slowly begin to understand each other's perspectives. They realize that they both have the same passion for music and for giving back through their art. By the end of the story, they not only make up but also plan future collaborations.
Maybe they had a falling out over creative differences. Jay Park wanted to experiment with a more edgy and modern sound, while 2PM was more focused on their traditional pop - dance style. Years later, a young trainee who idolizes both of them decides to write a song that combines both styles. The trainee approaches them separately to ask for their help. At first, they are hesitant, but as they get involved in the process, they start to respect each other's views again and make up, even performing the song together at the trainee's debut showcase.