Perhaps the story could start with her transformation into a ghoul due to some dark magic gone wrong. As a female Harry Potter - turned - ghoul, she might then be on a quest to reverse the transformation. Along the way, she could meet other ghouls and learn about their culture and society, all while still having her ties to the wizarding world and the people she cares about there.
Maybe Harry Potter, as a ghoul, has to hide his true identity from his friends at Hogwarts. He might struggle with his newfound nature while still trying to fight against the dark forces in the wizarding world.
Perhaps the plot could involve Fem Harry Potter's transformation into a ghoul being a result of some dark magic experiment gone wrong. She then has to find a way to reverse it while facing discrimination from some in the wizarding community who fear ghouls. Along the way, she could discover new magical abilities related to her ghoul form and use them to her advantage.
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.
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.
It could be really interesting. Maybe the wizards in Harry Potter world have to face the ghouls from Tokyo Ghoul. The magic spells could be used to fight against the kagune of the ghouls. For example, the Stunning Spell might stun a ghoul temporarily, giving the wizard a chance to escape or attack further.
One idea could be a new student arrives at the ghoul school who has a special power that can either save or endanger the school. For example, the ability to communicate with the ghosts that haunt the school in a way no one else can.
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.
There could be an older, wise ghoul teacher who serves as a mentor to the students. This character could have a lot of knowledge about the school's history and the ways of the magical world of ghouls.
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.
In some Harry Potter fanfiction, ghouls are often portrayed as creepy and somewhat menacing creatures. They might be lurking in the attics of old wizarding houses, like the one at the Weasley's. They are usually depicted as less intelligent than wizards but with an instinct for self - preservation and a certain wildness about them.