One common theme is identity. Harry has to figure out who he is now as a ghoul in a world that knew him as a wizard. Another theme is acceptance. He has to deal with whether others will accept him in his new form.
A big theme is often isolation. As a ghoul, Harry may find himself isolated from his former friends and the wizarding community. Also, power and control. Discovering his new powers as a ghoul and learning to control them is often explored in these fanfictions.
One common theme is mystery. Ghouls are often depicted as mysterious creatures in the Harry Potter series, and fanfictions tend to explore that further. For example, their origin and their purpose in the Hogwarts castle are often questioned and explored.
One common theme is the struggle between two different worlds. Since Harry Potter and Tokyo Ghoul have very different settings, the fanfictions often explore how a female Harry Potter would adapt to the dark and dangerous world of Tokyo Ghoul. Another theme could be power and identity. How does her magical abilities from the Harry Potter world interact with the kagune powers in Tokyo Ghoul? And how does she redefine her identity in this new context.
Well, many 'Naruto half ghoul fanfiction' stories share the theme of isolation. Naruto may feel isolated due to his half - ghoul nature, being different from everyone else in the village. Another theme is the search for a cure or understanding. He may be trying to find out how he became a half - ghoul and if there's a way to reverse it. Additionally, the theme of power corruption can be present. As Naruto gains these new and potentially dangerous powers, there's a risk that they could corrupt him, and the stories often explore how he resists or succumbs to that temptation.
In 'naruto ghoul school fanfiction', a recurring theme is the exploration of the unknown. Naruto is constantly exploring the mysteries of the ghoul school, like its hidden rooms and the secrets of the ghouls' powers. Another theme is the fight against prejudice. Since Naruto is different from the ghouls, he has to deal with the prejudice some ghouls have towards him, and he also has to overcome his own prejudices about the ghouls.
Power struggle is a common theme. You have the super - powered beings from Prototype and the ghouls from Tokyo Ghoul, all vying for control or survival in a merged world.
One common theme is the struggle for identity. Female Kaneki, being both human and ghoul, constantly has to figure out who she really is. This is often explored through her interactions with both humans and ghouls, and how she feels like she doesn't fully belong to either group.
One common theme is power combination. Since both Naruto and Tokyo Ghoul have unique power systems, fanfics often explore how the ninja techniques and kagune powers can be used together. Another theme is the clash of cultures. The shinobi way from Naruto and the harsh reality of the Tokyo Ghoul world are very different.
Romance is also a popular theme. It could be between different ghoul girls or with other characters from the related universe. For example, a love story between a ghoul girl and a mysterious outsider. There are often themes of acceptance too, as the ghoul girls might have to deal with being different from the norm.
The theme of redemption can also be present. Rize's actions towards Kaneki were quite cruel in the original story. Fanfictions may attempt to give her a chance at redemption, perhaps through her relationship with Kaneki. This could involve her showing remorse for what she did and trying to make amends in some way.
One common theme is love and sacrifice. Kaneki and Touken's relationship is often depicted as a deep, selfless love. They might be willing to sacrifice their own safety or desires for the other. For instance, Kaneki could put himself in danger to protect Touka from a powerful enemy.