It could be that the sister received some false information about Percy. Perhaps someone told her that Percy was planning to harm her or their family. Without verifying it, she made the hasty decision to abandon him. Another possibility is that the sister had her own dreams and ambitions that she felt couldn't co - exist with having Percy in her life. So she left him to pursue her own goals.
Maybe the sister had some dark secrets that she was afraid Percy would find out. For example, she could be involved in something illegal or dangerous, and to protect Percy from getting dragged into it, she chose to abandon him.
Well, in such a fanfic, perhaps Percy ends up in a new camp or place full of demigods he doesn't know. He has to prove himself without his mom's support. He could befriend some unlikely characters who help him understand more about his mother's disappearance. And in the end, he might find that his mom left to protect him from a greater threat that he now has to face on his own.
Well, it could make Percy grow up really fast. He might have to learn to fend for himself in ways he never thought before. He could become cynical about family relationships. Maybe he would start to view the world as a place where people are bound to leave you, and this could shape his interactions with others in a negative way, like always keeping people at arm's length.
In a 'Naruto abandoned for his sister' fanfic, perhaps there's a prophecy that only one of them can bring peace to the village. The elders, misinterpreting it, choose the sister and abandon Naruto. Naruto then goes on a journey outside the village, meets new friends and allies, and discovers new powers. Meanwhile, the sister is having her own struggles within the village, like dealing with the pressure of being the 'chosen one' and realizing that Naruto's abandonment might not have been fair.
One possible reason could be jealousy. Maybe his sister is jealous of Percy's special abilities or the attention he gets. Another reason might be that she is forced to abandon him due to some external threat or danger that she believes will harm her if she stays with Percy. Or perhaps she has been brainwashed into thinking that Percy is a bad influence or a danger to her.
In a Percy Jackson baby sister fanfic, she could have some really cool adventures. Maybe she discovers she has her own unique powers early on, like being able to communicate with sea creatures in a different way than Percy. She could also get into trouble by wandering into the wrong part of the camp, like the restricted areas where the more dangerous magical items are kept.
In such a fanfic, Naruto might initially be filled with sadness and confusion. He could become more withdrawn at first. But as the story progresses, he might find strength within himself and use the abandonment as a motivation to prove his worth, regardless of the yaoi elements in the story.
One possible plot could be Percy feeling a deep sense of betrayal and loneliness. He might struggle with his self - worth as he wonders why his sister left him. This could lead him on a journey to find answers about his family and his own identity, perhaps even uncovering secrets about his demigod heritage that his sister knew and he didn't.
One possibility is that Percy relives his life and focuses on training more intensively. He could learn new skills or magic earlier, which would change the course of his adventures. Maybe he would be more strategic in battles, and as a result, save more people and gain more respect in the demigod community.
An 'abandonment fanfic' is a type of fan - created fiction. It often involves scenarios where a character is abandoned, either by friends, family or in a more general sense like being left alone in a particular situation. For example, in a fanfic based on a superhero story, a sidekick might be abandoned by the superhero, leading to a whole new set of adventures and character development for the sidekick as they struggle to cope with the abandonment.
It could be a new powerful monster that was sent after Percy because his mom was no longer there to protect him. Maybe a monster that has a grudge against Percy's family.