It could also be because of jealousy. For example, if Annabeth was spending a lot of time with another character, perhaps a new demigod who showed great potential. Percy, being a bit insecure at times, might misinterpret her intentions and get angry.
One possible reason could be a misunderstanding. Maybe Annabeth made a decision without consulting Percy, like choosing a quest that she knew was dangerous but didn't tell him until it was too late. Percy might feel left out and mad about it.
It could strain their relationship a great deal. Their friendship and possible romantic relationship is based on trust. If Percy is mad, that trust is shaken. They might start avoiding each other, not sharing secrets like they used to.
It could be because of a misunderstanding. In the fanfic, perhaps Annabeth was seen talking to an old acquaintance who Percy doesn't trust. He might jump to conclusions and get angry with her without really knowing the whole story. Like, if he thought she was plotting something behind his back with that person.
One possible reason could be Percy's recklessness. He often jumps into dangerous situations without fully thinking them through, and Annabeth, being the more strategic one, might get frustrated and yell at him for endangering himself and others.
One reason could be jealousy. Maybe in the fanfic, Annabeth gets more attention or praise for her skills and Percy feels left out or overshadowed, which turns into hatred. Another possibility is that there's a rift caused by their different approaches to solving problems. If Annabeth's logical thinking clashes too much with Percy's more instinctive ways, it could lead to resentment.
Maybe he likes it because he has a deep connection with Annabeth in the original story and the fanfic allows him to see different interpretations of their relationship.
Another possibility is that Percy made a really stupid mistake that endangered himself or others, and Annabeth, being the more level - headed one in some ways, slapped him to snap him out of his foolishness. For instance, if he rushed into a dangerous situation without a proper plan, Annabeth's slap could be a wake - up call.
Well, it could be due to a misunderstanding. Maybe Percy thought Annabeth did something wrong regarding a quest, like made a decision without consulting him. In fanfics, authors often play with such relationship dynamics.
One possible reason could be jealousy. Maybe she sees Percy getting more attention or praise than her in the fanfic world, and that envy turns into betrayal. Another reason might be a misunderstanding. For example, if there's some misinformation spread about Percy that makes Annabeth believe he's done something really bad.
Well, it could be that Annabeth constantly corrects Percy in front of others. For example, when Percy is making a plan to defeat a monster, Annabeth keeps interrupting and saying his plan is all wrong. This public humiliation might make Percy mad.
Another way Percy could react is by giving Annabeth the silent treatment. He wouldn't talk to her for a while, which would be really difficult for Annabeth as they are usually close. Percy would just go about his business, ignoring her attempts to communicate until he feels she has truly understood how much she has angered him.