In some pokemon sun and moon oc fanfiction, the OC is an outsider who comes to Alola with a different set of values about pokemon training. For instance, an OC from a region where pokemon battles are more brutal. In Alola, they learn about the gentle and harmonious way of training. Their growth is not just about becoming a stronger trainer but also about changing their perspective on pokemon and the relationship between humans and pokemon.
A common storyline in pokemon sun and moon oc fanfiction is the OC having a special connection with a legendary pokemon. Let's say an OC who discovers a secret bond with Tapu Koko. This connection gives them unique powers or insights. They might have to protect the Alola region from a new threat that the regular trainers and kahunas are unable to handle alone. This often involves the OC learning about the ancient lore of Alola and using it to their advantage.
One interesting storyline could be an OC who is a new trainer in the Alola region. They start with a unique starter pokemon not typically found in the official games and their journey is about proving that this pokemon can be as strong as the traditional starters. For example, an OC with a Rockruff that has a special ability. They face challenges like the Island Trials in ways that are different from the main game characters, making new friends and rivals along the way.