Self - acceptance is a very prevalent theme. The two Kanekis need to come to terms with their own existence and their relationship with each other. Identity crisis is also common. They both represent different aspects of Kaneki's identity and the fanfic often explores how to reconcile these different identities. Additionally, the theme of power and control can be seen, as they may fight over who gets to be in control in certain situations.
One interesting female Kaneki fanfiction could be one where she forms an unexpected alliance with a group of ghouls from a different territory. In this story, she might use her unique perspective as both human and ghoul to bridge the gap between different ghoul factions. It could explore her internal struggle in a new light as she tries to maintain her humanity while also fitting into the ghoul world.
One possible fanfiction could be where Kaneki, after fully mastering his ghoul powers, becomes a sort of protector in the ghoul world. He could use his strength to keep the balance between humans and ghouls, defying the traditional enmity. He might be able to create new rules that both sides can abide by, making the world a more harmonious place for both species.
In a fanfiction where Kaneki is overpowered, he could have the power to heal the rift between humans and ghouls in a more radical way. He could use his extreme strength to force the humans to accept the existence of ghouls and also make the ghouls understand the importance of not preying on humans. His overpowered abilities would be like a shockwave that shakes the very foundation of the existing relationships and rebuilds them in a more positive way. For instance, he could create a safe zone where both humans and ghouls can live together without fear, and his overpowered presence would ensure that no one breaks the peace.
I've heard of a fanfic named 'Eyes of the Self'. In this one, the two Kanekis are constantly at odds, yet they also have a deep understanding of each other. It's really well - written, with great descriptions of their internal battles. There's also a fanfic that's more action - oriented called 'Battle of the Kanekis' where they fight against a common enemy while also dealing with their own relationship. And 'The Kaneki Bond' is a heart - warming fanfic that shows the bond between the two Kanekis growing over time.
One common theme is identity. Since it's a female version of Kaneki Ken, the fanfiction often explores how her gender affects her identity as a ghoul. Another theme is relationships. There are different takes on how she interacts with other characters like Touka or Hide.
One popular 'kaneki ken fanfiction' story could be those that explore his transformation in more depth. For example, some might focus on his mental state during the different stages of becoming a ghoul. Another could be about his relationships with other characters like Touka, showing their interactions in new and different scenarios that weren't fully explored in the original work.