Probably other demigods would interact with Percy. Maybe some demigods who are in need of a more stable influence in their lives would seek out Percy. Also, characters like Grover might find Percy in Hestia's care and there would be a reunion. And the gods and goddesses who are associated with the concept of home or family in Greek mythology, like Demeter, could also have interactions with Percy.
In this fanfiction, Percy could interact with nymphs and minor deities associated with Hestia's realm. They could teach him about the more subtle aspects of nature and the magic related to hearth and home. Additionally, if there are any threats to Hestia's domain or Percy himself, he might interact with heroes or guardians from Greek mythology who come to their aid.
Definitely Annabeth. She and Percy have a strong relationship, and Hera's possessiveness would surely disrupt that. Also, other demigods at Camp Half - Blood could interact with Percy. They might sense that something is off with Percy due to Hera's actions and try to help him or at least figure out what's going on. And of course, the gods themselves might interact with Percy. Some gods might side with Hera, while others might oppose her possessiveness over a demigod like Percy.
Obviously, Percy would be one of the main characters. Chaos, who raises him, would also be very important. There might also be some other primordial beings that interact with Percy during his upbringing.
Well, Annabeth would definitely be one. She's always been by Percy's side, and in this fanfiction, she might be a bit worried about Percy being the champion of Nyx. She could be trying to help him while also being cautious of Nyx's motives.
Obviously, Percy and Hades will interact a great deal. Percy will also likely interact with the Furies, as they are servants of Hades. They could be like his protectors or trainers in some sense. Another character could be Nico di Angelo, since he has a connection to Hades as well. They could bond over their shared relation to Hades.
The interaction could also be more action - oriented. Suppose they are all in a dangerous situation, like a powerful dark wizard from the Naruto world has somehow entered the world of Percy Jackson and is causing chaos. Naruto would use his combat skills and jutsus, Percy would rely on his demigod powers like controlling water and his swordsmanship, and Hestia could use her divine powers to protect them or provide strategic advice on how to defeat the enemy.
The theme of protection is often present. Hestia protects Percy from various threats. Also, there's the theme of change. Percy's place in the demigod world changes as he is now associated with Hestia. This can lead to different relationships with other characters like the other demigods and the gods. He might be seen as an oddity at first but then respected for his unique upbringing.
The plot could involve Percy being raised away from the typical demigod chaos under Hestia's care. He may be trained in the ways of maintaining harmony and peace. Hestia could use her powers to shield Percy from some of the more dangerous aspects of the demigod world, and in turn, Percy might become a sort of ambassador for her values among the other demigods, promoting the importance of a stable home environment and the bonds that come with it.
Draco Malfoy would be a likely character. Given his Slytherin status, he would likely have a complex relationship with Percy. He might start off as hostile, seeing Percy as an outsider, but then they could end up having to work together for some reason.
One great 'Percy raised by Hestia' fanfiction is 'A New Home with Hestia'. In this story, Percy's relationship with Hestia is beautifully depicted. Hestia takes him in and nurtures him, and Percy grows into a different kind of hero under her care. It shows how Percy's values are influenced by Hestia's warm and motherly nature.
Main characters Percy will interact with? Well, he'll surely have some sort of encounter with the Fates. Since time travel is involved, the Fates would have a role to play. Maybe he has to convince them not to interfere too much with the changes he's making. Also, he could interact with the Titans in a more personal way. Not just as enemies as in his own time, but perhaps understand their motives better by being in the past with them. And don't forget about the minor gods. In the past, they might have had more influence or different relationships, and Percy could get caught up in all of that.