One possibility is that the fanfiction could explore the growth of Percy and his friends' relationships. Since they have crushes on him, they might be more motivated to be better versions of themselves. For example, they could study harder if Percy values intelligence, or become more athletic if that's what Percy admires. At the same time, Percy might be flattered but also a bit confused, and he'd have to navigate through his own feelings about his friends while maintaining the friendships.
He could also be very kind and gentle in his reaction. Percy might not want to hurt his friends' feelings, so he'd try to let them down easy if he doesn't feel the same way. He might say something like 'You're a great friend, and I value our friendship so much' to show that he cares about them but not in that romantic way. On the other hand, if he has some hidden feelings for one of them, he could start to show more interest in return, like spending more time alone with that friend.
In such a fanfiction, Percy might help Hades with some internal underworld issues. For example, dealing with rebellious spirits. Since they are friends, Percy could use his unique abilities and knowledge of the modern world to assist Hades in modernizing certain underworld operations, like record - keeping. It could also lead to interesting interactions with other underworld deities who might be suspicious of this new friendship.
A simple thing that could happen is that Nancy tries to befriend Percy's friends to get closer to him. This way she can be around him more often.
Well, in the fanfiction, Percy's friends might be in awe of Annabeth's intelligence. She could lead them in some sort of adventure or strategy planning. Maybe they initially have some misunderstandings but then come to respect her as they see how much she means to Percy.
Well, she might initially seem a bit out of place. Since she's a demigod and used to the world of Camp Half - Blood. But she could quickly adapt and start showing off her intelligence. Maybe she'd impress Percy's mortal friends with her knowledge of architecture and ancient history.
Well, in the fanfiction, Percy might initially seem a bit out of place among Annabeth's mortal friends. He could accidentally do something that reveals his demigod nature, like reacting too quickly to a threat that normal people wouldn't notice. Maybe he'll be super strong when helping them move furniture or something.
In the fanfiction, Annabeth's friends might be initially shocked. They could start teasing Percy in a friendly way, or some might be secretly attracted. Maybe there would be some blushing and awkward conversations.
Perhaps they would have a food fight. Percy could use his powers to control the mess, like making the flying food bits form cool shapes in the air. His friends would be laughing hysterically.
Well, in some fanfictions, Annabeth's mortal friends might be initially in awe of Percy. They could be amazed by his powers like controlling water. Maybe they'll be a bit scared at first but then grow to like him as they see how he cares for Annabeth.
In the fanfiction, Percy's mortal friends could find themselves in dangerous situations. Since demigods often attract trouble, the mortals might get caught up in battles against monsters. However, they could also learn a great deal from the demigods, like how to be brave in the face of fear and how to use their wits when in a tight spot. The demigods, in turn, might learn about the simplicity and normalcy of mortal life from Percy's friends.