One plot idea could be that the female OC is on a quest to find a hidden treasure that was once her family's. Along the way, she has to outwit other pirates who are also after the treasure. Another idea is that she is wrongly accused of a crime she didn't commit in a pirate port and has to clear her name while also dealing with the various pirates and scoundrels in the area.
A plot could involve the female OC being a spy for a powerful pirate lord. She is sent to infiltrate another pirate crew, but she starts to have second thoughts as she gets to know the crew members. She then has to decide whether to continue with her mission or betray her original master. Another idea is that she discovers a long - lost pirate ship that is haunted. With the help of some other pirates, she tries to uncover the secrets of the ship and the treasure it might hold while facing the ship's ghosts and other perils.
Well, start with her motivation. What drives her in the dangerous world of Pirates of the Caribbean? It could be revenge against a certain pirate who wronged her family. Then, for her skills, she might be good at disguising herself, which would be very useful in pirate dealings. In terms of her relationships, she could have an old mentor who taught her the ways of the sea. This adds depth to her character. And don't forget about her flaws. Maybe she's a bit too impulsive at times, which gets her into trouble.
You can start by looking on fanfiction.net. It has a large collection of 'Pirates of the Caribbean' fanfictions, including many with male OCs. Just use the search bar and type in relevant keywords like 'Pirates of the Caribbean male OC' and you'll get a list of stories.
One great 'Pirates of the Caribbean' male OC fanfiction is 'The Lost Pirate'. It features a male original character who has a mysterious past and finds himself entangled in the world of Jack Sparrow. The story is full of exciting sea battles and treasure hunts.
Love and friendship are also common themes. The mermaid OC could fall in love with a pirate or form a strong friendship with a member of the crew. In some fanfictions, this relationship helps bridge the gap between the mermaid's world and the pirates' world. For instance, in a story, a mermaid OC's love for a pirate makes her risk everything to save him from a cursed situation.
A great plot for Beast Pirates OC fanfiction could be an OC who is a doctor with a mysterious past. The OC joins the Beast Pirates under false pretenses, claiming to be able to create a super - soldier serum using Devil Fruit powers. As they work within the group, they secretly try to find a way to cure the madness that seems to be a part of the Beast Pirates' nature. Along the way, the OC has to deal with the various power - hungry and unpredictable members of the pirates, like Jack and Queen, while also hiding their true intentions.
Your OC could be a ranger who has a vendetta against a powerful orc chieftain. The orc has been raiding villages and killing innocents. The OC sets out on a mission to hunt down the orc. Along the way, they get involved in a larger conflict between the forces of good and evil. They meet other characters from the Lord of the Rings world, like Aragorn or Legolas. This plot allows for a lot of action and character development as the OC battles their personal enemy while also contributing to the greater fight against Sauron.
One plot idea could be that she has to stop a villain who is trying to steal her immortality. Another is that she discovers a new threat to the world that only she, with her long - lived experience, can understand. Maybe she teams up with a group of heroes who initially don't trust her because of her immortality.
For an Inuyasha male OC fanfiction plot, consider this. The male OC is an artist who can paint things that come to life. He gets caught up in the chaos around the Shikon Jewel when one of his paintings accidentally becomes a powerful demon. Now he has to work with Inuyasha and the others to defeat it. Or he could be a demon slayer who has a personal vendetta against a particular type of demon that is also involved in the Shikon Jewel saga. His presence disrupts the group's dynamics at first, but they soon realize they need his skills. Another idea is that he's a messenger from another dimension who brings news of a greater threat that will affect not only the Inuyasha world but also other dimensions.
One plot idea could be that the male OC is a detective hired to investigate strange disappearances in the Black Butler world. He starts to suspect that there's a supernatural force at work and teams up with the main characters to solve the mystery. Another idea is that he's a nobleman's son who has a secret identity as a vigilante, fighting against the corrupt nobles. He might cross paths with Ciel and Sebastian when they're on a mission related to the same nobles.
A plot could involve the male OC being related to one of the scientists who worked at the lab. He comes to Hawkins to find out what really happened to his relative. Along the way, he teams up with the kids and they uncover a conspiracy that goes deeper than they thought. Or perhaps the male OC is an artist and he starts having visions of the Upside Down through his art, which leads him on a journey to figure out what they mean.