One common theme is the forbidden love between a human and a vampire. Since vampires are often seen as dangerous and different, it creates a lot of tension when they fall in love with a human, like in many BTS vampire fanfics.
Another theme is the power struggle. Vampires in these fanfictions usually have certain powers, and V's character has to either learn to control his powers or face challenges from other powerful beings. For example, there might be a conflict between different vampire clans where V has to prove himself. It adds an element of action and suspense to the story.
One common theme is the struggle between their vampire nature and human emotions. Since BTS are vampires in these fanfictions, they often have to deal with their bloodlust while also having feelings for humans or each other. Another theme is the idea of a coven hierarchy. There's usually a leader among them and different roles for each member.
The relationship can start with curiosity. The vampires are curious about this human child who is so different from their usual prey. The child, on the other hand, might be in awe of the vampires' powers and appearance. This mutual interest can lay the foundation for their relationship.
One popular BTS V vampire fanfiction is 'Vampire's Love for V'. It has an interesting plot where V is a vampire with a complex personality. The story is filled with mystery and romance.
Love and acceptance is a big theme too. The BTS members gradually come to accept JK for who he is, vampire or not. There are heartwarming moments where their love for each other overcomes the fear and uncertainty associated with JK's new identity. And sometimes, there are romantic undertones in the relationships as well, not just platonic love but also a deeper, more complex form of love that is unique to the vampire - human dynamic in these fanfictions.
Love and acceptance is also a big theme. The nerdy character usually comes to love JK for who he is, vampire and all. It shows that love can transcend differences. And JK often has to accept his own vampire nature while also being in a relationship with someone from the 'normal' world. It's about two people finding common ground in their differences.
Often, there's a theme of transformation. The 'nerd' characters might transform in some way, either physically or mentally, because of their encounter with the vampires. And of course, friendship is a big theme. The BTS members, whether as vampires or not, usually have strong bonds with each other and with the 'nerd' characters in the fanfiction. This friendship can be tested by the secrets and the vampire nature.
One common theme is the struggle with his new vampiric nature. He might be confused about his new powers and instincts. For example, he could be fighting the urge to drink blood in some stories.
One possible plot could be that JK, as a vampire, struggles to control his newfound thirst for blood while still trying to be part of BTS. He might be afraid of hurting his bandmates and tries to isolate himself at first. But then, through their strong bond, the other members help him come to terms with his new identity and they find a way to keep his vampire nature a secret from the public.