One good storyline could be an OC who is a new transfer student at Gekkoukan High School and quickly catches Mitsuru's attention due to their unique abilities in the Dark Hour. The OC could initially be a bit of an outcast but gradually forms a strong bond with Mitsuru as they work together to face Shadows. Another idea is a fanfiction where the OC has a special connection to Mitsuru's family history, perhaps uncovering secrets that were long forgotten and helping Mitsuru come to terms with her heritage. There could also be a storyline where the OC is from a rival organization but ends up falling for Mitsuru and has to choose between loyalty to their group and their new - found feelings.
Well, a great storyline might involve the OC being a healer in the Persona world. Mitsuru, being a strong leader, often gets injured in battles. The OC starts patching her up and during these moments, they start to develop feelings for each other. As the story progresses, the OC discovers a way to enhance Mitsuru's Persona powers, but it comes with a great risk. They have to decide whether to take that risk or not. Also, the OC could be an artist who can see the auras of Personas. When they see Mitsuru's Persona, they are inspired to create a powerful work of art that has some unforeseen magical properties that help in the fight against Shadows.
To write a compelling OC in relation to Mitsuru, first, give the OC a distinct personality. For example, if Mitsuru is more reserved and serious, the OC could be outgoing and humorous to create an interesting dynamic. Also, give the OC a unique backstory. Maybe they grew up in a different country or had a special encounter with a Persona at a young age that shaped their abilities. Their goals should also be clear, whether it's to become a strong Persona user like Mitsuru or to find a way to end the Dark Hour once and for all.
One great story could be about their friendship evolving into a deeper understanding during a difficult mission in Persona 3. They might start to rely on each other more than ever, realizing how much they value one another's skills and personalities.
In some persona 4 oc fanfiction, an OC might be a detective who is secretly investigating the strange happenings in Inaba. This OC could have their own set of skills and resources, and as they dig deeper, they discover connections between the real world and the TV world that the main characters haven't noticed yet. Their investigations could also put them in danger and lead to some intense action scenes.
In some fanfiction, there might be a scenario where they get into an argument over a decision regarding the SEES group. Maybe Mitsuru wants to take a more cautious approach while Makoto is eager to be more aggressive. But through this conflict, they learn to compromise and strengthen their bond as leaders of the group.
Their relationship often develops through shared battles. As they fight side by side against the Shadows in Tartarus, they start to trust each other more. They rely on each other's strengths, like Makoto's physical combat abilities and Mitsuru's strategic thinking.
You can try fanfiction websites like Archive of Our Own (AO3). It has a large collection of fan - created works, and you're likely to find some great 'persona 3 mitsuru x yukari fanfiction' there. Just use the search function to look for it specifically.
One interesting storyline could be about the Phantom Thieves exploring a new, mysterious Palace that has different rules than the ones they've encountered before. Maybe it's a Palace where time is constantly shifting, making it difficult for them to plan their heists.
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.
One idea could be creating an OC who is a transfer student with a unique past related to the Dark Hour. For example, they might have had a family member affected by Shadows long before coming to the school. Another idea is an OC with a special ability that doesn't quite fit the normal Persona - using skills that are more about mental manipulation rather than direct combat. And you could also have an OC who is initially a skeptic about the whole Persona thing but slowly gets drawn into it.
Well, you could have an OC that is a skilled hacker who gets involved with the Phantom Thieves by accident. They might have a Persona that represents a famous code - breaker from history. Also, an OC who is a foreign exchange student from a country with a very different cultural background could bring in new elements to the fanfiction. Their Persona could be influenced by their home country's folklore. Maybe an OC who is a prodigy artist and uses their art skills to create powerful items in the Metaverse, with a Persona related to a great artist from the past.