Use unique character traits. Give the male OC some really interesting hobbies or skills that are not typical. For the milf teacher, make her teaching style or her views on education different. For example, the male OC could be a talented artist who uses his art to express his feelings for the teacher.
One way is to play with the setting in an unexpected way. Instead of the usual school setting, what if they meet in a summer school on an island? The change of scenery can bring new challenges and opportunities for their relationship. Another idea is to give the characters strong voices. Let the male OC have his own unique way of speaking and thinking, and the same for the teacher. This will make them more memorable.
Focus on character development. Make your OC have unique traits and backstory that interact well with Obito's character. For example, if your OC has a strong sense of justice, it can contrast or complement Obito's more morally ambiguous actions.
Focus on character development. Give your OC a distinct personality, backstory, and goals. For example, if your OC has a troubled past that affects how they interact with Digimon, it will make the story more engaging.
Create a unique backstory for your OC. Give them a motivation and a history that ties into the Dragon Ball universe in an interesting way. For example, if your OC has a vendetta against a certain villain that Kefla has also faced, it can create an instant connection between them.
Give your OC a unique backstory. For example, if they come from a strange or mysterious place, it will make them more interesting. Also, give them a distinct personality trait like being extremely shy but super competitive when it comes to the Running Man games. Another way is to give them a special skill or ability that no one else in the Running Man world has.
Give him a unique appearance. For example, if your fanfiction is set in the world of The Little Mermaid, your male OC could have hair that changes color depending on his mood, like the sea creatures. This will make him visually distinct.
Focus on unique character traits for your OC. Give them a distinct personality, like being extremely shy but also having a hidden wild side. Also, create a fresh take on the relationship between Lucifer and the OC. Instead of the typical love - hate, make it more of a slow - burn friendship that gradually turns into love.
Use dialogue effectively. Have Darly and the OC have conversations that are not just about their feelings but also about their views on the world, how to deal with threats, and their hopes for the future. This will make their relationship seem more real. Also, add some mystery to the OC. Don't reveal everything about them at once. Let the readers be curious and keep reading to find out more about the character.
Incorporate real historical events into the story. Since 'Rurouni Kenshin' is set in a historical context, adding details about the Meiji Restoration or other relevant events can make the story more immersive. Also, focus on the character development of both the OC and Kenshin. Show how they change and grow because of their interactions.
Play with the relationships. Instead of just having the OC be a sidekick, create complex relationships. Maybe the OC has a romantic interest in one of the Sailor Scouts' enemies, which causes a rift in the group at first but then leads to a deeper understanding of the enemy's motives and a new way to defeat them. It's all about adding unexpected twists and turns to the story.
Create a unique backstory for your OC. Give them special skills or powers that set them apart. Also, make their personality really engaging.