In a fanfiction, Naruto could be training in a secluded area and Yandere Koneko stumbles upon him. She immediately falls for his spunk and the fact that he doesn't give up easily. Yandere Koneko then tries to insert herself into Naruto's life by bringing him food and small gifts. Naruto is initially confused but then realizes she has a rather extreme way of showing affection and has to gently set boundaries.
One idea could be that Naruto somehow gets trapped in a dimension where Kaguya has become a yandere for him. She tries to keep him there all to herself, while Naruto has to figure out a way to escape and also deal with her obsessive behavior.
One common theme is possessiveness. The yandere characters in these fanfictions often show extreme possessiveness over Naruto or other characters. For example, they might not allow the object of their affection to be around other people.
Naruto might be initially confused. He's used to people being friendly or at least straightforward with their intentions. So when Mikoto starts showing her yandere side, like getting overly possessive, Naruto would probably be like 'What's going on?'. He could try to talk to her and understand her behavior at first.
Naruto would probably be really confused at first. He's used to a loving mother figure, not a yandere one. He might try to talk to her and understand why she's acting so strangely.
Maybe the fanfiction could start with Kushina being resurrected in some way and immediately developing this yandere love for Naruto. Naruto, being the kind - hearted person he is, tries to understand her but is constantly baffled by her extreme behavior. For example, she gets jealous when Naruto spends time with his sensei, Kakashi, and tries to sabotage their training sessions.
One common theme is the struggle for the oc against the yandere Naruto's possessiveness. For example, in many stories, the oc is an independent character who values freedom, but Naruto's yandere nature tries to restrict that. Another theme is the exploration of Naruto's character transformation. Normally he is seen as a bright and friendly character, but in these fanfics, his yandere side brings out a darker, more obsessive part of him. There's also often a theme of secrecy and danger, as the oc may be afraid to expose Naruto's true nature to others in the village.
One common theme is possessiveness. Since Naruto is in a yandere state, he is extremely possessive of Sakura. Another theme is the distortion of love. His love for Sakura is not the normal kind but rather a bit extreme and obsessive.
Start with a strong inciting incident. For example, Kaguya could be resurrected with a yandere - like obsession for Naruto due to some dark magic. Then, build up the conflict as Naruto tries to resist her advances while also dealing with the chaos she causes in the ninja world.
One possible plot could be that Mikoto, in her yandere state, becomes obsessed with Naruto. She might try to keep him away from his friends and training, believing that only she can protect him. For example, she could use her Sharingan abilities to spy on Naruto's interactions with others like Sasuke or Sakura, and then interfere when she feels Naruto is getting too close to them.