Love triangles are also quite common. Imagine a character from KHR falling in love with a vampire from Vampire Knight while another character from either series is also in love with one of them. It adds a lot of drama and tension to the story.
Another theme is the struggle for power and control. The Vongola family in KHR is all about power dynamics, and in Vampire Knight, the vampire clans also have their own power struggles. When combined in fanfiction, it can lead to some epic battles and political intrigue.
One popular theme is the crossover of powers. For example, how the flames from KHR would interact with the vampire abilities in Vampire Knight. It's fascinating to see how the different power systems could either complement or clash with each other.
I really like 'A Hidden Bond'. In this fanfic, it delves deep into the relationships that could form between the characters of KHR and Vampire Knight. It's full of emotional moments and some great action scenes. The author does a wonderful job of making the two different universes blend together seamlessly.
A common theme is adventure. They often go on adventures together, exploring hidden parts of the vampire world. This could involve seeking out ancient vampire artifacts or trying to find a safe haven for a group of outcast vampires.
Some fanfictions focus on Hinata's role in the complex social hierarchy of the vampires. Since Vampire Knight has different vampire clans and power structures, Hinata might find herself in the middle of political intrigue. For example, she could be a key figure in uniting different clans or causing a rift depending on her actions. And of course, the theme of love triangles or complex romantic relationships involving Hinata is also very popular in these fanfictions.
One of the most popular themes is the power of their love. Their love is often depicted as strong enough to overcome the differences between vampires and humans. For example, in many fanfictions, they face opposition from vampire society but their love endures. Another theme is redemption. Kaname, with his complex past, is often shown on a path of redemption through his love for Yuki. It gives his character more depth.
Another theme is redemption through love. Some fanfiction might focus on a vampire who has done bad things in the past but finds redemption through their love for another character. For instance, a vampire who has killed humans may change his ways because of his love for a human or another vampire, and this change is often a central part of the story.
The theme of forbidden love is also quite common. Since vampires in Vampire Knight have their own set of rules and hierarchies, a yaoi relationship might be seen as going against the norm. Writers often play with this idea, showing how the characters deal with the secrecy and potential consequences of their relationship.
Zero is often very popular. His complex character, being a vampire hunter with vampire blood himself, makes him full of contradictions and depth. Fans are intrigued by his internal struggle between his human side and the vampire instincts within him.
One of the popular themes is the complex relationship between Zero and Yuki. In many fanfics, it delves deeper into their unspoken feelings. Another theme is the struggle against the vampire world's rules. Since the Vampire Knight series has a strict vampire - human hierarchy, fanfics often explore how Zero and Yuki might break or change these rules. Also, the theme of self - discovery is common. As both characters grow throughout the series, fanfics expand on their individual journeys of finding out who they really are and how their relationship with each other affects that discovery.
Well, a common theme is the idea of the 'outsider'. In Twilight, Bella often feels like an outsider in the vampire world, and in Vampire Knight, Zero is an outcast among the vampires and humans due to his unique situation. Also, the theme of secrecy is important. The vampires in both stories have to keep their true nature a secret from the general human population.
One popular theme is crossovers. Writers like to combine the two universes and see how the characters interact. For example, seeing how the guardians from KHR would react to the Clow Cards in Card Captor Sakura's world.