One plot idea could be that the OC is a new student at Yuyu Hakusho's school. Kurama, being yandere, becomes instantly obsessed with her. He starts leaving her little gifts, like rare flowers from the demon world. Another idea is that the OC has some special power that Kurama wants to protect at all costs, even if it means getting rid of anyone who gets too close to her. Maybe the OC is initially unaware of Kurama's true nature and thinks he's just a friendly classmate.
A plot could revolve around a tournament in the Yuyu Hakusho universe. The OC is a competitor, and Kurama is determined to make sure she wins, using any means necessary. He might sabotage other opponents in secret. Or perhaps the OC gets injured during a fight, and Kurama's yandere side goes into overdrive, vowing to take revenge on whoever hurt her. He could also be possessive and not let the OC train with anyone else, fearing they might steal her away.
To develop their relationship, start with small interactions. For example, the OC could accidentally bump into Kurama in the school hallway. Kurama, being yandere, is immediately intrigued. Then, gradually build up the intensity. Maybe the OC asks Kurama for help with homework, and he uses this as an opportunity to get closer to her. He could also share some of his secrets from the demon world, which makes the OC trust him more.
Another plot point could be a competition among demons. The OC plant demon is entered into a tournament of sorts, and Kurama decides to be her coach or partner. They have to train together and face various opponents. Along the way, they develop a strong bond, not just as comrades in battle but also as friends or even more, and they learn more about each other's strengths and weaknesses.
There's this fanfiction called 'Kurama's Unlikely Companion'. The OC in it is a bit of an outcast, and Kurama is initially hesitant about getting close. But as the story progresses, they form a deep connection. The story is filled with action and drama, and the relationship between Kurama and the OC is very well - explored.
To write a great Kurama x OC fanfiction, you need to focus on character growth. The OC should grow and change because of their relationship with Kurama, and vice versa. For instance, if the OC is initially afraid of demons, Kurama could help them overcome that fear. Use vivid descriptions to bring the world of Yu Yu Hakusho to life, from the spooky forests to the bustling demon markets. This will draw readers into the story and make them care about the relationship between Kurama and the OC.
One idea could be that the OC is a new hero in the DC universe. The yandere Enchantress becomes obsessed with the OC because of their unique powers. She starts to manipulate situations to be around the OC more, like causing villains to attack near where the OC is so she can 'help' and get closer to them.
One plot idea could be that the OC is a new villain in Gotham. Harley Quinn becomes yandere for the OC because of their unique style of chaos. She starts to stalk the OC, leaving little gifts that are both disturbing and endearing, like a dead bird with a love note.
A common theme could be the witch OC's struggle to fit into the 'Yuyu Hakusho' world. Since it's a different kind of character in that universe.
One idea could be an OC who is a half - demon from a previously unknown demon clan. They could have unique powers that both intrigue and worry the main characters. For example, the power to manipulate time on a small scale during battles.
Well, perhaps the OC reborn as Kurama tries to find a way to coexist peacefully with the jinchuriki in a different way than in the original story. They could use their unique perspective to broker better relationships between the tailed beasts and the humans. Maybe they also try to uncover secrets about the origin of the tailed beasts that were previously unknown.
A really interesting plot could be that the OC is from a different dimension and accidentally ends up in Youko Kurama's world. They start off as strangers but gradually form a bond as the OC tries to find a way back home, and Youko Kurama helps them while also learning about this new and strange being. This can involve a lot of world - building and exploration of different cultures or powers.