Perhaps there's a prophecy that involves both Percy and Artemis in the high school. It could be about a hidden power within the school that only they can unlock together. They have to navigate high school politics, friendships, and enemies all while trying to figure out the prophecy and save the day.
One idea could be a quest where Percy and Artemis have to team up to rescue a group of demigods captured by a powerful new enemy. Maybe a Titan who has found a way to drain the powers of young demigods. Percy's skills in water manipulation and combat, combined with Artemis's archery and her connection to the moon, would make for an exciting adventure as they face various challenges along the way.
One idea could be Percy having to deal with a new type of mythical creature that has infiltrated Goode High School. Maybe a group of mischievous satyrs that are causing chaos in the school cafeteria by stealing all the food and Percy has to use his skills to stop them without revealing his true identity to the normal students.
One idea could be Percy having to hide his demigod powers at high school while dealing with a bully who unknowingly has ties to a minor Greek god. This would create a lot of tense drama situations.
Perhaps there's a mystery at Ares High School where strange things keep happening, like students getting sudden bursts of uncontrollable strength. Percy, suspecting it has something to do with Ares, investigates and discovers an ancient artifact hidden on campus that's causing the chaos. He then has to find a way to stop it without getting caught by the school authorities or Ares' minions.
Perhaps there's a powerful artifact that can only be activated by a father - daughter bond between Percy and Artemis. They are forced to work together to find and use this artifact to stop a great catastrophe. Along the way, they face many challenges. Percy has to deal with the fact that Artemis is a very different kind of 'daughter' compared to what he might expect, and Artemis has to come to terms with having a father figure for the first time in her existence.
One plot idea could be Fem Percy Jackson joining Artemis' hunt. Since Percy has her own set of skills and powers, it would be interesting to see how she adapts to the life of a hunter. Maybe she could bring a new perspective to the group and help them in ways they haven't thought of before.
One interesting plot idea could be Percy having to team up with Artemis on a quest that involves an ancient artifact that has the power to disrupt the balance between the gods. Maybe it's an artifact that can control the tides in a way that endangers both land and sea. Another idea is a story where Artemis is somehow in danger and Percy has to use his skills and connection to the sea to save her while also dealing with her hunters who are initially suspicious of him. And a third plot could be about Percy and Artemis finding a new, unknown demigod who has powers that are a mix of the sea and the moon, and they have to figure out how to train this demigod and protect them from those who would misuse their powers.
One idea could be Percy having to protect Artemis from a new and powerful monster that has a special ability to track her. Another could be Percy and Artemis teaming up to retrieve a lost magical artifact that is important for the balance of the world. Maybe Percy has to enter Artemis's domain in the forest and face challenges there while protecting her.
One idea could be that the child has unique powers inherited from both Percy and Artemis. For example, the ability to control water like Percy and also have a strong connection with the moon and hunting like Artemis. Another plot could involve the child trying to find their place in the demigod world, being part of two very different lineages. They might face challenges from both sides, some who are suspicious of their mixed heritage.
Here's a more complex plot. In the fanfiction, Percy discovers that there's a prophecy related to the Hunters of Artemis that could change the balance of power between the gods. He's drawn into this mystery as the Hunters suspect he might be the key to either fulfilling or preventing the prophecy. Along the way, he forms an unexpected bond with one of the hunters, which causes some internal conflict among the group, as they have sworn off relationships with males. This would create a lot of drama and interesting character dynamics.