Most one piece fanfiction dont go after fishman island because of insufficient canon material so fan fiction author hits a hard block,, and well they make MC so powerful that he rules the world after defeating the emperor and destroying world government or semi destroy it??
I already had assumptions that once the mc rules the one piece world he will meet other sytem user such as entities that also have systems from other worlds.☹️
After almost one years follow this story from star i just sad that this fanfic is drop event after i now it probably drop because you already not up long time
nightseeker