Some great ideas for Detective Conan OC fanfiction are as follows. You could create an OC who is a hacker and can access all kinds of restricted information to help solve cases. They might be a bit of a loner but have a soft spot for Conan and his friends. Another concept is an OC who has a photographic memory for maps and locations. This would be really useful in tracking down suspects or finding hidden places related to the cases. And finally, an OC who is a psychic (in a world where it's a very rare and not fully understood ability). They could sense things about the victims or the criminals that normal detective work couldn't uncover.
One idea could be creating an OC who is a master of disguise, like Conan, but with a unique backstory. Maybe they are from a different country and have their own reasons for getting involved in the detective work in Japan. Another idea is an OC that has a special gadget - something that hasn't been seen in the original series yet, like a device that can analyze poisons instantly. And a third idea could be an OC who is a childhood friend of Shinichi's that has some hidden talents related to solving mysteries that come to light after his transformation into Conan.
Well, you could have an OC that is a childhood friend of Shinichi who has a photographic memory. This OC could recall small details from their past that end up being crucial in solving current cases. Or perhaps an OC who is an expert in a very specific field, like ancient languages, and Conan has to rely on this OC's knowledge when a case involves old inscriptions or manuscripts. Also, an OC who has a connection to the Black Organization, either as a former member trying to reform or someone unknowingly involved in their plans, could add a lot of drama to the fanfiction.
One idea could be a crossover with Sherlock Holmes. Conan could meet Holmes in London and they could solve a complex mystery together. Holmes' deductive skills and Conan's modern knowledge would make for an exciting combination.
One idea could be that Harry Potter travels to the world of Detective Conan. He could use his magic to help Conan solve some cases that seem impossible with just normal detective skills. For example, he might use a spell to reveal hidden clues or to track down a suspect who has magically disappeared.
One idea could be that Harry Potter and Conan end up in the same magical - mystery world. Harry uses his magic skills while Conan uses his detective skills to solve a case that involves dark wizards and a powerful, mysterious artifact. Another idea is a crossover where the characters from Hogwarts visit Conan's world, and they all have to work together to figure out a series of strange disappearances that seem to be related to a new type of magic or potion.
One idea could be a fanfic where Conan has to solve a mystery within a virtual reality game world. Another could be a story where he teams up with a new character who has a unique detective skill that complements his own. Maybe a fanfic about Conan traveling back in time to solve a mystery related to his parents' past.
One interesting Detective Conan OC fanfic could be 'The New Detective in Beika'. It introduces a new original character who has unique deductive skills and gets involved in Conan's cases. Another great one is 'OC's Adventure in the Black Organization'. It gives a different perspective as the OC tries to infiltrate the Black Organization. And 'OC and Conan's Team - up' is also good, showing how an OC and Conan work together to solve mysteries.
One idea could be a story where Conan and Kid Lemon team up to solve a mystery that involves a rare and precious gem. Another could be a scenario where Kid Lemon is wrongly accused of a crime, and Conan has to use his detective skills to prove his innocence. Maybe they could also be in a situation where they have to work together to stop a villain who is targeting both of them.
A more complex plot could be that there is a secret connection between the two worlds. A powerful artifact from the wizarding world has been stolen and ends up in the hands of a criminal in Detective Conan's world. This leads to a race between the wizards and Conan's team to retrieve it. Along the way, they discover that there are ancient prophecies that tie the two worlds together and that the fate of both depends on getting the artifact back. This could involve a lot of character interactions, like Hermione and Ran becoming friends and sharing their knowledge, or Ron and Conan bonding over their love for food while also trying to solve the mystery.
Another idea is that they are at a masquerade ball. Shinichi is disguised as someone else, but Ran still senses his presence. They dance together and as the music reaches a crescendo, Shinichi reveals himself and kisses Ran. This would add an element of mystery and glamour to the story, as they are surrounded by other masked guests who are oblivious to their true identities.
One idea could be an OC who is a detective trainee and teams up with Detective Pikachu to solve a mystery in a new part of the Pokemon world. Maybe they are investigating a series of disappearances of rare Pokemon. Another plot could involve an OC with a special ability to communicate with certain types of Pokemon that Pikachu can't, and together they use their combined skills to stop a villain who wants to use these Pokemon for evil.