Well, in a Tokyo Ghoul and Harry Potter crossover fanfiction, there could be a character who is both a ghoul and a wizard. This character would have to struggle with the dual nature of their existence. On one hand, they have the magic of the wizarding world, but on the other, they have the hunger for human flesh as a ghoul. They might use magic to try and control their ghoul instincts, like using a spell to suppress the urge to attack people.
A plot might involve a magical accident that transports some of the Tokyo Ghoul characters into the wizarding world. Kaneki could end up at Hogwarts and be sorted into a house. He'd struggle to hide his ghoul identity while also trying to find a way back home. At the same time, the wizards are intrigued by his unique abilities and some, like the more power - hungry ones, might try to use him for their own gain. Harry Potter and his friends would then have to decide whether to trust Kaneki or not.
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.
The storyline could be really interesting. Maybe the ghouls could be a new kind of dark creature in the Harry Potter world. The characters from Tokyo Ghoul, like Ken Kaneki, might attend Hogwarts. He could struggle with his ghoul nature while trying to fit in with the wizards and witches. The magic in the Harry Potter universe could also have an impact on the ghouls' abilities, perhaps suppressing or enhancing them.
Hermione would probably be extremely curious about the ghouls. She'd want to study their biology, especially the kagune. She might even try to find a way to use her magic to help the half - human, half - ghoul characters like Kaneki deal with their identity crisis.
One way the worlds could collide is through a magical accident. Maybe a spell in the Harry Potter universe goes wrong and opens a portal to the Tokyo Ghoul world. The wizards could be shocked to see the ghouls with their kagunes. And the ghouls would be equally surprised by the magic of the wizards.
One idea could be a crossover where a character from Harry Potter accidentally enters the world of Tokyo Ghoul. Medusa could be incorporated as a dark force or an ancient evil that has somehow influenced both worlds. Maybe she has the power to turn ghouls into stone, which throws the already complex ecosystem of Tokyo Ghoul into chaos. And in the Harry Potter side, her presence could be related to dark magic spells that are long forgotten.
One idea could be a crossover where a vampire from the Harry Potter universe somehow ends up in the world of Tokyo Ghoul. Maybe a vampire who was hiding in the Forbidden Forest gets transported to Tokyo and has to adapt to the new rules of the Tokyo Ghoul world, dealing with ghouls and the CCG. This could lead to some interesting power dynamics as the vampire's magic might be a new factor in the Tokyo Ghoul ecosystem.
Harry Potter and Ken Kaneki would be a really interesting pairing. Harry has faced so much darkness in his life and has a strong sense of justice. Kaneki, too, has been through a lot and is trying to find his place in a world that fears him. They could bond over their shared experiences of being different and having to fight against powerful enemies.
The combination of Rize Kamishiro and Lord Voldemort would be quite the duo in a crossover fanfiction. Rize is a powerful and somewhat sadistic ghoul, and Voldemort is the most feared dark wizard. They could team up to cause mayhem in both the ghoul and wizarding worlds. Their combined power would be a huge threat, and it would take the combined efforts of the heroes from both universes to stop them.