One idea could be that Harry, while on a magical journey, stumbles into the world where Moka lives. He discovers that his magic has some unexpected interactions with her vampire powers. For example, his spells might be able to temporarily nullify her blood - lust in a new and unique way.
Another plot could be a story where Naruto is somehow lost in Moka's world. He has to adapt to the new rules and customs while also trying to find a way back home. Along the way, he befriends Moka and they learn from each other's strengths. For example, Naruto teaches Moka about the importance of friendship and loyalty in his ninja world, and Moka shows Naruto how to use his chakra in new and unexpected ways in her world.
A Moka crossover with 'Star Wars' would be cool. Picture Moka as a Jedi or a Sith. Her vampire abilities could be translated into unique Force - related powers. Or a crossover with 'My Hero Academia'. Moka could be a student in the hero school, and her vampire powers could be seen as a very special 'quirk'. She might have to face discrimination from some students who are scared of her vampiric nature at first.
One idea could be Tsukune and Inner Moka going on a magical adventure in a hidden realm. They might encounter strange creatures and have to work together to overcome obstacles. Another plot could be a mystery where they try to solve a strange occurrence in their school that seems to be related to the supernatural world they inhabit. And perhaps a plot where they get lost in time and have to find their way back while also dealing with their feelings for each other.
There could be a fanfiction where Tsukune and Moka accidentally switch bodies. This would lead to a lot of comical situations as they try to adapt to each other's lives. Moka in Tsukune's body would have to deal with human school life and Tsukune in Moka's body would have to handle the vampire society. Additionally, a plot about a mysterious prophecy that involves both of them and their fates being intertwined with the future of the vampire - human relations could be really engaging.
One idea could be that Naruto, with his kitsune powers, and Moka end up in a parallel dimension where they have to work together to find a way back home. They face strange creatures and have to learn about each other's abilities along the way.
One idea could be that the OC is a new student at the school. They accidentally discover Moka's vampire secret and instead of being afraid, they are intrigued. This could lead to a friendship where the OC helps Moka navigate human - vampire relations in a more modern world. Another plot could involve the OC having a special power that is somehow connected to Moka's vampire heritage, and together they have to face a common enemy.
One plot idea could be that Vampire Tsukune and Inner Moka have to team up to fight a new and powerful enemy that threatens the entire monster school. They start to train together and during this time, they discover new powers within themselves and also grow closer on an emotional level.
Maybe Inner Moka has to go to the Naruto world for some reason, like to find a rare ingredient for a potion that only exists there. Naruto helps her navigate his world and in the process, they learn about each other's cultures and powers. Along the way, they also have to face some of Naruto's enemies who are interested in Inner Moka's vampire abilities.
Maybe there's a story where an ancient evil is threatening all of their worlds. Naruto, Moka and Kurumu are chosen as the representatives to fight against it. At first, they have trouble working together due to their different personalities and ways of doing things. But as they face more and more difficult battles against the evil, they start to understand and trust each other more, and eventually combine their powers to defeat the great threat.
Perhaps a story where Moka and Akasha are transported to the Naruto world. They are initially confused but then start to adapt. Moka could use her vampire allure to charm some of the ninja, which causes some chaos. Akasha, on the other hand, tries to find a way back home. Naruto befriends them and helps them understand the ways of his world. Along the way, they uncover a conspiracy in the Naruto world that is related to a mysterious lemon - scented substance that has strange effects on ninja and vampires alike.