An OC could be a foreign exchange student who has a special power similar to Celty's headless state. Maybe they can disappear at will or have some sort of telepathy. Their presence in Ikebukuro disrupts the existing balance as different groups try to figure out what their power means and how to use it to their advantage.
One idea could be an OC who is a new informant in Ikebukuro. They get caught up in the power struggles between the Dollars, Yellow Scarves, and Saika. For example, they might start off as a neutral party but end up having to choose a side when their own safety is at stake.
A male oc could be a supernatural being, like a half - vampire or something similar. He comes to Ikebukuro in search of a cure for his condition. Along the way, he befriends some of the main characters, such as Mikado and Kida, and together they uncover secrets about his origin that are linked to the long - forgotten history of the city.
An OC could be a street artist in Ikebukuro who uses their art to tell the stories of the various gangs and groups in the area. This OC could interact with Celty as they both have an interest in the unique aspects of the city. They might start a project to document Celty's presence in a positive way, which could draw the attention of the Dollars and other factions.
One plot idea could be that Naruto characters end up in Ikebukuro. For example, Naruto himself could be searching for a new type of ninja tool that he heard can only be found in Ikebukuro. Meanwhile, the gangs in Durarara start to notice this strange, orange - clad boy with strange powers. Another idea is a character swap where some of the Durarara characters gain ninja abilities and get involved in Naruto - style battles in their own world. Maybe Celty could use her shadow powers in a more ninja - like way, like stealth and quick attacks.
Well, a great plot for Durarara Shizuo x Reader fanfiction could be set during a festival in Ikebukuro. The reader gets lost in the crowd and Shizuo, with his intimidating presence, clears a path for them. This initial encounter could lead to more interactions as the reader starts to bring out the softer side of Shizuo. Maybe the reader is also involved in some sort of underground activity in Ikebukuro that Shizuo is trying to protect them from, and in the process, they fall in love. It could also be that the reader has a special power or ability that Shizuo discovers, and this discovery deepens their connection.
One plot idea could be that a character from Tokyo Ghoul ends up in Ikebukuro (the setting of Durarara). For example, Kaneki could find himself in the middle of the Dollars' activities. He might initially be confused by the different kind of chaos compared to the ghoul world. Another idea is that Celty's head mystery somehow gets intertwined with the ghouls' existence. Maybe there's a ghoul who has knowledge about her head, and this leads to an alliance between Celty and some of the Tokyo Ghoul characters to find out the truth. A third plot could involve the gangs in Durarara getting involved with the ghoul - human conflict in Tokyo Ghoul. They might try to take advantage of the situation for their own gains, but end up getting more than they bargained for as they learn about the true nature of ghouls.
One idea could be a story where Aoba and Mikado have to team up to solve a mystery in Ikebukuro. Maybe there's a new gang causing trouble and they use their different skills and connections to figure out who's behind it.
One idea could be creating an OC who has a unique power related to time manipulation. They could be from a different dimension and end up in the Avengers' world. Another idea is an OC who is a master of ancient magic and teams up with Doctor Strange within the Avengers group. Maybe an OC that is a super - intelligent android created by a villain but has a change of heart and joins the Avengers.
You could create an OC for your Persona OC fanfiction who is an artist. This artist OC could use their art as a way to understand and even manipulate the Metaverse. For example, they might draw scenes from the Metaverse that give clues about upcoming events or hidden locations. Their art could also be a form of therapy for other characters who are struggling with their dual lives in the real world and the Metaverse.
Perhaps an OC who is a half - human, half - beast creature. This OC could struggle with acceptance in both the human and beast - kin societies. They end up meeting the main characters during their adventures and learn to embrace their unique identity with the help of the group, while also adding their own combat skills, which are a blend of human strategy and beast - like strength, to the team.
One idea could be to explore the Riddler's origin story from the perspective of your original character (OC). Maybe your OC is a detective trying to solve the mystery of the Riddler's first crime spree. Another idea is to have your OC be a sidekick of the Riddler, either willingly or by being forced into it. They could then have a complex relationship where the OC tries to influence the Riddler's actions for better or worse.