There could be a group of anti - military rebels outside the military. They see the military as a tool of oppression and are constantly causing trouble. Percy might have to deal with them, either through combat or trying to negotiate and understand their point of view.
He might use his demigod powers to become a super soldier. His skills in combat and his ability to control water could give him an edge in various military operations, like amphibious assaults.
Perhaps Percy joins a special unit in the military. In this unit, he discovers some sort of conspiracy or mystery within the military structure. This could lead him on a journey to uncover the truth while still fulfilling his military duties. He might also face some moral dilemmas along the way as he tries to do what's right for the military as a whole.
His other friends from Camp Half - Blood would have mixed reactions. Some would be proud of him for wanting to serve and protect in a different way. Others might think he's crazy for leaving the world of demigods and getting involved in mortal military affairs. They know he has a duty to the demigod community, and joining the military could put that in jeopardy. But overall, they would support him because they know Percy always follows his heart and they trust his judgment.
It could be a jealous friend. Maybe another demigod who is envious of Percy's powers or his popularity among their peers. This friend might see an opportunity to get Percy out of the way and so betrays him.
In 'percy joins the romans fanfiction', it could start with Percy being transported to the Roman world by some magical or divine means. Once there, he has to adapt to their strict military - like structure. He might have conflicts with some of the Roman leaders who are skeptical of his loyalty. However, he overcomes these by showing his courage and loyalty to the greater good of the Roman demigods, and finally joins them in their battles against common enemies.
Well, one possibility could be that Percy uses his skills from his own world to help SHIELD in combat situations. Maybe his ability to control water could be useful in, say, putting out fires caused by super - villains or in creating barriers against enemy attacks. He could also interact with SHIELD agents in a really interesting way, like teaching them some of his own combat techniques.
Well, it could be a really wild ride. Percy joining Gaea would be such a shock to his friends. They would probably think he's been brainwashed. And Percy himself might be in for a rude awakening when he sees Gaea's true intentions. She could be using him to get to other demigods, or to start a war between the gods and the demigods. He'd have to figure out a way to break free from her influence before it's too late.
The story of 'percy joins the hunters fanfiction' could start with Percy being invited to join the Hunters for some special reason. Once he joins, he has to deal with the fact that the Hunters are mostly female and have their own traditions. He may find himself in the middle of internal Hunters' politics. For example, some Hunters might be skeptical about his presence, while others see his potential. His journey within the Hunters could also lead to self - discovery, as he learns more about himself and his place in this new group, all while going on quests and battling against various foes.
In 'percy joins the hunt fanfiction', it could be that Percy joins to find someone or something. He might be on a quest to rescue a friend who has been captured by the creatures that the hunt is targeting. His loyalty to his friends would drive him to take risks and face the unknown challenges of the hunt.