In some fanfictions, Percy's sister might hurt him emotionally by betraying his trust. For example, she could share his secrets with others, making him feel exposed and betrayed.
Communication is key. Naruto and his sister could sit down and have an honest conversation about what's bothering him. They could clear up any misunderstandings that led to his hatred.
The story could end with Naruto realizing his hatred was misdirected. After some big event or revelation, he discovers that his brother and sister actually care for him deeply. They all reconcile and become a closer - knit family.
Perhaps she's a sister who was thought to be dead but actually survived. She could have been corrupted by the experiences she had while being 'dead'. When she returns, she blames Percy for not saving her properly. This false blame leads her to betray Percy. She could start spreading rumors about Percy being a coward or a bad leader among the demigod community.
Well, it could be because of jealousy. Maybe his sister gets more attention from their parents or is better at something that Percy wishes he was good at.
The implications are mainly negative. It promotes an unethical and immoral relationship that goes against basic human values. It can also be disturbing for readers who have a normal sense of right and wrong.
This is a rather disturbing concept as incestuous relationships are not acceptable in society. However, there might be some very dark and inappropriate fanfictions out there that explore such themes, but I would not recommend seeking them out as they go against moral and ethical norms.
Percy might be initially confused. He may not understand why his half - brother has such strong negative feelings towards him. He could try to talk to him to resolve the issue, thinking it's just a misunderstanding.
One common plot could be that the sister has a different ideology. For instance, she might believe in a more radical approach to achieving peace in the ninja world compared to Naruto's more inclusive and forgiving way. This difference could lead to clashes and eventually Naruto's hatred. Another plot could be a power struggle. If the sister is extremely powerful and uses her power in a way Naruto doesn't approve of, like being cruel to weaker ninjas, it could make Naruto hate her.
One possible reason could be jealousy. Maybe the sister is getting more attention from their parents or at Hogwarts. For example, if she is a star student and Harry feels overshadowed.