Maybe a plot where Tsukune and his harem enter a magical tournament. They have to compete against other supernatural groups. Tsukune would need to figure out how to use each harem member's unique abilities to their advantage in different challenges.
One interesting plot idea could be Tsukune having to protect his harem members from a new powerful vampire threat that has emerged in the school. This would involve a lot of action scenes where Tsukune uses his growing powers.
A plot could be centered around Tsukune trying to find a way to make his relationship with each member of his harem more equal. There are different personalities in the harem, and some might feel left out or jealous. Tsukune would need to plan special dates and activities for each to strengthen their bonds.
Well, a simple plot could be that Female Tsukune is new to the school and accidentally catches the eyes of several interesting characters, thus forming a harem. They each try to court her in their own unique ways. A vampire might use his charm and knowledge of the night to impress her, a witch could use magic to create beautiful things for her. As the story progresses, Tsukune has to figure out who she really likes among them while also dealing with the jealousy and drama that comes with a harem situation.
One plot idea could be Tsukune's further exploration of his unique powers in the Rosario Vampire world. He might encounter a new type of enemy that challenges his abilities in ways he hasn't faced before. Another could be a love triangle involving Tsukune, Moka, and another character, creating a lot of drama and tension. Maybe Tsukune has to go on a quest to find a lost artifact that has significance in the vampire world, and along the way he discovers more about his own heritage.
One plot idea could be Tsukune and Ria going on a journey together to discover a hidden power within the Rosario Vampire world. This could involve them facing various monsters and challenges along the way, and their relationship growing stronger as they rely on each other.
A more romantic plot could involve Yukari developing deeper feelings for Tsukune and trying to confess her love in a world full of supernatural distractions and challenges. It could show how their relationship might develop in a different way from the original story.
One interesting plot could be Tsukune and Ruby going on a secret mission within the Yokai Academy. They might have to face a new type of supernatural threat that neither of them has encountered before. This would test their skills and their relationship as they rely on each other to survive.
Well, a plot idea could be that Kurumu and Tsukune get trapped in a time - loop. They keep repeating the same day over and over, and in the process, they learn more about each other's true selves. Each repetition of the day brings them closer together as they figure out how to break the loop.
Some fanfictions focus on what - if scenarios. What if Tsukune was actually a powerful vampire from the start? How would that change his relationship with Mizore? There are also fanfictions that deal with challenges to their relationship, like a rival for Tsukune's affections who is also a powerful monster. This creates a lot of drama and tension in the story as Mizore has to fight for Tsukune's love.
One interesting plot idea could be that Naruto somehow gets transported to the Rosario Vampire world and has to adapt to its unique rules. He could end up forming a harem with the female characters from the Rosario Vampire series, like Moka. Maybe he uses his ninja skills to protect them from other threats in that world.
Fanfiction could also center around Mizore and Tsukune training together. Since they both have different powers, they could learn from each other. Tsukune could teach Mizore about human resilience and determination, while Mizore could show Tsukune how to better control his powers, especially when it comes to the more vampiric aspects. Their training sessions could be filled with both comical and intense moments.
One idea could be Tsukune learning a new and powerful vampire ability. For example, he discovers he can manipulate shadows in a way unique to him, which helps him in battles against other supernatural foes in the Rosario Vampire world.