Tsukune could leave Mocha because of a misunderstanding. For example, he overhears something that makes him think Mocha is involved in something bad, so he decides to distance himself from her. But as he leaves, he starts to question if he made the right decision as he still has feelings for her.
One possible plot could be that Tsukune leaves Mocha due to a sense of duty. Maybe he realizes he has a greater mission in the world of Rosario Vampire that he can't pursue while being with Mocha. He might leave to protect her from the dangerous elements in his life.
In this fanfiction, Tsukune may leave Mocha to find himself. He has been through so many changes since being in the Rosario Vampire world, and he might feel that he needs time alone to figure out who he really is. He might think that being with Mocha is holding him back from this self - discovery journey.
One possibility could be that Tsukune's death is a sacrifice to save his friends. In the Rosario Vampire world, he has made many friends and perhaps in the fanfiction, a powerful enemy threatens them all. Tsukune, being the selfless character he is, might give his life to ensure their safety. For example, if a dark and ancient vampire or a powerful monster attacks the school, Tsukune could use his unique powers (a combination of human and vampire abilities) in a final, all - out attack that costs him his life.
The plot could revolve around the baby's discovery of its powers. It might start with the baby accidentally using a new power, like being able to phase through walls or having super - strength. This would catch Moka and Tsukune off - guard, and they would then need to find out how to control these powers. Along the way, they could meet other characters from the Rosario Vampire series who either offer help or pose a threat to the family.
Well, one possibility could be that Tsukune, being a vampire in the Rosario Vampire universe, somehow gets involved with the Sub Zero world. Maybe he has to face off against Sub Zero's enemies using his vampire powers. For example, he could use his super strength and speed to combat the ice-based attacks of Sub Zero's foes.
A plot could be that Tsukune has a strange dream about Akasha one night. In the dream, she is in some kind of danger. When he wakes up, he can't shake off the feeling. So, he starts to search for any signs of trouble around Akasha. As he gets closer to her, he finds that there are some dark forces at work that are indeed targeting Akasha, and he has to use his own unique abilities (maybe some new ones he has developed) to protect her.
In a fanfiction plot, perhaps Tsukune gets into trouble with a group of bullies at school. Moka comes to his rescue and in the heat of the moment, they kiss. This kiss could be a moment of realization for both of them about their true feelings. After that, they start to secretly meet and have more romantic encounters. But they have to keep it a secret because of the rules at the school. Their relationship develops as they try to find a way to be together openly, with the kiss being the starting point of their journey.
Tsukune's vampire form in fanfiction can vary greatly. Some authors might focus on the emotional aspect of him dealing with this new side of himself. He could struggle with the urge to feed on blood, or he might embrace it as a part of his new identity. Additionally, his relationships with other characters, especially Moka, can be significantly affected by his vampire form.
One possible fanfiction could be about Mizore and Tsukune going on an adventure together in the world of Rosario Vampire. Maybe they have to face a new kind of supernatural threat that has emerged in the school. They could use their unique abilities, Mizore's ice powers and Tsukune's growing vampire - human hybrid powers, to combat this threat and protect their friends.
One possible fanfiction could be about Nekonome and Tsukune going on a secret adventure in the school grounds. Maybe they discover a hidden passage that leads to a place full of magical artifacts. Nekonome's feline instincts could help them navigate through the dangerous parts while Tsukune's growing powers could be used to protect them from any threats.
One possible fanfiction could be about Akasha seeing Tsukune's unique nature among humans and vampires. Maybe she decides to test him in various ways, putting him in situations that make him question his own beliefs and values. Tsukune, in turn, could be both intrigued and a bit frightened by Akasha.
One possible fanfiction could be about Tsukune and Akasha's first encounter. Maybe Tsukune, being new to the vampire world, stumbles upon Akasha in a hidden part of the school. Akasha, with her powerful presence, initially intimidates Tsukune. But as they start to interact, Tsukune realizes there's more to her than just her fearsome reputation.