The settings of the two could also play a big part. Tokyo is a modern, bustling city in Tokyo Ghoul. The Rosario Vampire school is a unique setting filled with different supernaturals. If they crossed over, we could see the Tokyo Ghoul characters having to adapt to the school setting or vice versa. For example, Ken Kaneki could find himself in the middle of a battle between different Rosario Vampire factions while trying to hide his ghoul identity.
Another aspect is the power systems. Ghouls in Tokyo Ghoul have their kagune and different combat abilities. In Rosario Vampire, the characters have their own unique powers like Moka's vampire strength. If there was a crossover, there could be epic battles or even power - sharing situations. For instance, a ghoul might learn how to use some of the magic - like abilities from the Rosario Vampire characters to enhance their own fighting skills.
Well, one way the storylines could blend is through the character interactions. In Tokyo Ghoul, the ghouls have a complex society and set of rules. In Rosario Vampire, there are various supernatural beings. If the two universes crossed over, perhaps the ghouls' need for human flesh could be in conflict with the vampires' need for blood in Rosario Vampire. Maybe some characters from each side would form alliances to deal with this new, complex situation.
One way the storylines could blend is through a shared universe concept. For example, the unique powers in 'Tenchi Muyo' could interact with the vampiric elements of 'Vampire Rosario'. Maybe the characters from 'Tenchi Muyo' find themselves in the world of 'Vampire Rosario' and have to deal with the vampire politics and powers there. This could lead to interesting character developments as they adapt to a new and dangerous environment.
A new character could be a hybrid of a ghoul and a vampire. This character might have the strength and speed of both species. They could struggle with their dual nature, being attracted to both human blood and flesh but also having a sense of morality from both the ghoul and vampire worlds.
One possible plot could be a character from Tokyo Ghoul ending up in the world of Vampire Knight. Maybe Kaneki, with his unique ghoul powers, could interact with the vampires and hunters in Vampire Knight. He might initially be seen as a threat, but as the story progresses, they could find common ground in their struggle for survival in a world that fears them.
One way they could blend is through the characters' personalities. In Zootopia, Judy Hopps is determined and idealistic. In Ladybug, Marinette is kind-hearted but also has a secret superhero side. Maybe Judy could end up in Paris and team up with Ladybug to solve a mystery that involves both the animal world and the Miraculous world. For example, a villain could be using animal - themed Miraculous to cause chaos in both worlds.
In a Rosario Vampire Tsukune Ghoul fanfiction, Tsukune might face new challenges. He could be hunted by anti - ghoul organizations because they mistake him for a ghoul due to some new power he has acquired. This would force him to prove his innocence and also learn more about the world of ghouls in the process.
Well, in this crossover, the Survey Corps members like Armin would be fascinated by the intelligence of some ghouls. They might try to communicate with them to gain knowledge about their powers. Ghouls like Touka would be in a difficult situation. She would be in a world full of titans, which are much larger and more difficult to deal with than the CCG in her own world. She might have to learn new fighting techniques from the Survey Corps. And characters like Erwin would see the ghouls as a valuable asset, trying to recruit them to fight the titans.
Kaneki's kagune could be used in combination with Shinichi's parasite - enhanced physical abilities. For example, Kaneki could use his kagune to create a distraction while Shinichi uses his speed and strength to attack the enemy. Or they could work together in a more direct way, with Shinichi using his parasite - hand to hold an enemy in place while Kaneki delivers a powerful kagune strike.
The characters would interact in very interesting ways. For instance, Levi from Attack on Titan might be initially suspicious of the ghouls. But once he sees their combat abilities, he could try to recruit them or at least work with them. Kaneki, on the other hand, might be in awe of the Survey Corps' determination. He could learn a lot from their teamwork and discipline. And the ghouls' concept of a 'family' within Anteiku could be something that the soldiers of the Survey Corps might find strange but also endearing.
If we consider other characters, like Touka from Tokyo Ghoul, her combat skills combined with a parasite - like ability could be really interesting. Imagine if she had some of the regenerative abilities of a parasite. She could take more risks in battles. And for the parasites in Parasyte, if they could somehow access the kagune - like substances from ghouls, it might give them an entirely new form of attack or defense. They could potentially use it to create barriers or projectiles similar to how ghouls use their kagune.
The characters would interact in very unique ways. For example, Harry Potter might be initially cautious around the ghouls from Tokyo Ghoul. He's used to dealing with Voldemort and his Death Eaters, but ghouls are a completely different type of threat. Ken Kaneki, being a half - ghoul, could teach the wizards about the nature of ghouls, and in return, the wizards could show him some amazing magic spells.