The plot might focus on the struggle for identity that both Kaneki and Shinichi face. Kaneki is caught between his human and ghoul sides, while Shinichi has to deal with having a parasite in him. In the crossover fanfic, they could exchange their experiences and learn from each other. They might also encounter a new type of being that combines the traits of ghouls and parasites, which forces them to re - evaluate their own identities and how they fit into this new world of the crossover.
The plot could involve a shared threat that forces the Tokyo Ghoul and Parasyte universes to collide. Maybe a new type of organism emerges that is even more dangerous than ghouls or parasites. The characters would then have to combine their unique abilities to combat this threat. For instance, Kaneki's kagune and Shinichi's enhanced physical abilities with his parasite Migi could be used in tandem. This would create an interesting dynamic as they try to figure out how to work together while also dealing with their own internal struggles related to their inhuman natures.
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.
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.
One popular crossover idea could be with 'Attack on Titan'. Picture Tokyo Ghoul characters in the world of Titans, fighting alongside or against the Survey Corps. Another could be with 'Fullmetal Alchemist', where the alchemical concepts might interact with the ghoul powers. For example, an alchemist trying to find a way to cure the ghouls or control their kagune.
When writing a Tokyo Ghoul crossover fanfic, focus on character development. If it's a crossover with 'Fairy Tail', show how the Fairy Tail mages react to the existence of ghouls. Some might be scared, while others might be curious. Build a world where the two universes blend well. For example, in a city where Fairy Tail mages and ghouls co - exist, there could be new laws and power dynamics. And don't forget to add some emotional depth, like a ghoul falling in love with a human mage and the struggles that come with it.
The plot could involve the ghouls from Tokyo Ghoul being brought into the Avengers' world. Maybe the Avengers initially mistake the ghouls for new, dangerous threats. But as they learn more about the ghouls' situation, they might try to find a way to co - exist. For example, Kaneki could share his story with the Avengers, and they could be sympathetic. Then they could team up to fight a common enemy, like a new type of super - villain who wants to use the power of ghouls for evil purposes.
Well, it could be about Jedi or Sith characters finding themselves in the Tokyo Ghoul universe. Maybe a Jedi has to use the Force to deal with the ghouls' kagune. They might try to bring peace between humans and ghouls, like they do in their own galaxy with different species.
It depends on personal preferences. Some people might think Tokyo Ghoul is better for its original story and character development. Others might prefer Tokyo Ghoul:Re for its continuation and new plot twists.