The plot could be that the granddaughter has a special ability that the 13th chairman wants to utilize for the good of the Hunter community. So, he takes her under his wing to train her. As they train, they encounter various enemies who are after the granddaughter's power.
Well, perhaps the 13th chairman discovers that the granddaughter is related to a very important figure from the past in the Hunter x Hunter world. He then decides to protect her and in the process, they end up on a journey to uncover more about her family's past. Along the way, they form a strong bond, facing many difficulties like dealing with other Hunters who might have different motives regarding the granddaughter.
One possible fanfic could be about the adventures that the granddaughter gets involved in under the watchful eye of the 13th chairman. Maybe she discovers some hidden secrets within the Hunter x Hunter world with his guidance.
The plot could center on the 13th chairman's efforts to bridge the gap between different hunter groups. There are often various types of hunters with different goals and methods. The chairman might try to unify them to work towards a common good, like protecting the world from a new, unknown danger.
One possible fanfic could be about the journey of the 13th chairman in the world of Hunter x Hunter OC. It might explore their rise to power, the challenges they face within the complex Hunter Association. Maybe they have to deal with political intrigue, different factions vying for control, and also how they interact with the hunters. They could be introducing new policies or trying to reform the existing ones to better suit the changing world of hunters.
I'm sorry, I haven't read this '15th hunter chairman oc fanfic' specifically, so I can't explain its plot. But generally, in a fanfic, the plot might revolve around the original world setting of the 'hunter' concept, with the 15th hunter chairman as a central figure. It could involve his adventures, challenges he faces, relationships with other characters, and how the original elements of the hunter world are explored and expanded upon in the fan - created story.
I'm not sure as I haven't read it, but surely the 15th hunter chairman is one of the main characters. And since it's an 'oc fanfic', there are probably original characters created by the author that are also main characters. They could be friends, rivals, or subordinates of the chairman.
One possible plot could be that Killua decides to surprise Gon with breakfast in bed. He gets up early, sneaks into the kitchen, and tries to cook Gon's favorite meal. However, he's not very good at cooking, so there are a lot of comical mishaps. In the end, Gon wakes up to a messy kitchen but a very sweet gesture from Killua.
The plot might involve Naruto's unique abilities like shadow clones and Rasengan being combined with Nen abilities in the Hunter x Hunter world. For example, he could use his chakra to enhance his Nen attacks if he manages to learn Nen. And they could all be on a quest to find a way to get Naruto back to his own world while also dealing with some powerful villains who are interested in Naruto's power.
One idea could be a story where Pitou's brother is a human-turned-Chimera Ant. He has retained some of his human memories and is constantly in conflict with his new Chimera Ant instincts. Pitou tries to help him come to terms with his new existence while also dealing with the Hunter x Hunter world's chaos.
The plot could also involve her having unique nen abilities different from Hisoka's. She might be on a journey to understand these powers and in the process, cross paths with the main characters from Hunter x Hunter. Perhaps she forms an unlikely alliance with Gon and Killua, who initially are wary of her because of her relation to Hisoka, but later come to respect her for her own qualities.
One way to incorporate an OC into the plot of a Hunter x Hunter fanfic is to make them a part of an existing story arc. For example, if the fanfic is set during the Chimera Ant arc, the OC could be a new Hunter sent to help fight the Chimera Ants. They could have a special skill or knowledge that is crucial in the battle. Another way is to create a new story arc centered around the OC. Maybe they discover a hidden danger in the Hunter x Hunter world that the other characters are unaware of, and they have to convince Gon, Killua, and the others to join them in facing this threat.