Percy might be really shy and hesitant at first. He could blush and stutter, not expecting such a request from Annabeth.
He could also be a bit defiant and ask her why she wants him to do it. Maybe he's in a bad mood or just doesn't like being told what to do in that regard. But then, if Annabeth gives him a good enough reason, like she thinks he's hurt and needs to be checked, he might reluctantly comply. Another possibility is that he trusts Annabeth so much that he just does it without much question, knowing that she must have a valid reason. He might even make a joke about it to ease the tension, like 'Sure, but only if you buy me dinner first' or something like that.
Percy's reaction could be a mixture of confusion and curiosity. On one hand, he's confused as to why Annabeth would make such a request. But on the other hand, he's curious to see where this is going. He might look around to see if there are other people around, feeling a bit self - conscious. If he's in a more confident mood, he might take it off with a bit of a flourish, like he's showing off. Or he could be really cautious, slowly unbuttoning his shirt while keeping an eye on Annabeth to gauge her reaction, all the while his mind racing with different thoughts about what she could be up to.
One possible reason could be that she suspects Percy has some sort of mark or injury on his torso. Maybe they were in a recent battle or encounter and she wants to check if he's okay.
In the context of a fanfic, there could be a bet or a dare involved. Percy lost a bet or was dared to let Annabeth take his shirt off. This could lead to some humorous or interesting interactions between them as they both deal with the situation.
He could also playfully try to get it back, leading to a bit of a chase or a fun exchange between them. This would add some light - heartedness and interaction to the fanfic.
One possible scenario could be that Percy got injured and Annabeth needs to tend to his wounds on his torso, so she takes his shirt off. For example, he might have been scratched by a monster during a battle, and she has to clean and bandage the wound quickly.
Annabeth could be one of the main characters interacting with him. She might tease him about taking his shirt off, or she could be concerned if he's taking it off because of an injury. Their relationship is complex, and this situation could add a new layer to it.
Annabeth might be initially speechless. She'd look at Percy with a mix of disbelief and love. After a moment, she would throw her arms around him and say 'yes' while laughing. She would then start thinking about all the adventures they could have as a married couple and how they could build a future together in both the mortal and demigod worlds.
She might take it because she loves the smell of it. It has Percy's scent, which makes her feel close to him.
It could be a story where Percy takes his shirt off during a training session. Maybe he's getting ready for a really intense sparring match and removing his shirt is part of his pre - fight ritual to show his determination and focus.
She might be initially shocked. After all, seeing someone's abs unexpectedly can be a bit of a surprise.
Percy could meet the school bullies. And they might pick on him at first, but then be in for a big surprise when he shows his strength. Also, he might encounter some teachers who suspect there's something different about him. Maybe a science teacher who notices his quick reflexes during an experiment or a history teacher who is amazed by his knowledge of ancient mythology.