You could create an OC who is a ghoul investigator from a foreign country. This OC would bring different techniques and perspectives to the fight against ghouls. They might also face discrimination or misunderstanding within the Tokyo Ghoul universe due to being an outsider. For example, they could have a special weapon or training method that the local investigators haven't seen before.
One plot idea could be your OC being a new ghoul trying to find their place in the ghoul society. They might start at the bottom, having to learn the rules of the different ghoul groups and facing discrimination from more established ghouls. Another idea is that your OC discovers a secret about their transformation that no one else knows, like it was part of a secret experiment by the CCG. They then have to figure out what to do with this knowledge while also avoiding being caught by the CCG.
Another aspect could be his relationships. He might have a complicated friendship with a human who is aware of his ghoul nature. This relationship could be full of tension, as they both try to navigate the dangerous world where ghouls and humans are at odds.
Some plot ideas for Tokyo Ghoul female OC fanfiction include her being an outcast among ghouls due to her different beliefs. Maybe she believes in non - violence and tries to spread this message, which goes against the traditional ways of many ghouls. Or, she could be on a quest to find out the truth about her transformation into a ghoul. Was it an accident, or was she targeted? This could lead her to uncover secrets about the ghoul world that have been long buried.
A good plot also involves character growth. Have your male OC start as a naive ghoul and through his experiences, he becomes more cunning and powerful. This transformation can be the heart of the fanfiction, as readers watch him overcome obstacles and change for the better.
One possible plot could be that the oc is reborn as a ghoul in the Tokyo Ghoul world. They struggle to come to terms with their new identity and the need to feed on human flesh. They could try to find a way to co - exist with humans without causing harm, perhaps by joining Anteiku and learning from Kaneki and the others.
To create a compelling Ghoul OC in Tokyo Ghoul fanfiction, first consider their backstory. Maybe they were turned into a ghoul under tragic circumstances, like losing a loved one in a ghoul attack and then being turned. Their kagune is also important. It could be a unique shape or have special abilities, for example, a kagune that can change color to blend in with the environment. Their personality should be complex. They could be conflicted between their human side and the newfound ghoul instincts. For instance, they might still feel empathy for humans but also need to feed on them to survive.
A good plot could involve a human OC who is a doctor. They end up treating a ghoul who was severely injured in a fight. This starts a strange relationship where they try to understand the nature of ghouls better. As they get more involved, they learn about a secret organization within the ghoul world that is planning something big that could endanger all of Tokyo. The OC then has to decide whether to stay out of it or try to stop it. It's a plot full of moral dilemmas and action. Also, a plot where the human OC is an artist and they use their art to show the hidden side of the ghoul - human relationship could be interesting. Their art could either be a way to promote peace or it could stir up more trouble depending on how different groups react to it.
One idea could be a fanfic where a human character tries to form a peaceful co - existence pact with the ghouls. They might start by secretly helping a friendly ghoul and gradually work towards getting both sides to understand each other better.
One plot idea could be that the normal human OC discovers a secret organization that is trying to create a peace treaty between ghouls and humans. The OC gets involved in the negotiations, facing opposition from both sides. Another idea is that the OC is a detective who is investigating a series of ghoul - related murders and ends up getting too close to the truth and becomes a target. Or perhaps the OC is a doctor who tries to find a way to make ghouls live without having to eat humans.
There's also 'Tokyo Ghoul: OC's Unlikely Harem'. This one stands out because it delves deep into the psychological aspects of the OC being in a harem situation. It shows how he struggles with his feelings for different characters while also trying to survive in the dangerous world of Tokyo Ghoul. The character development is top - notch and the relationships feel very real.