Well, a plotline might involve Harry being hunted by those who oppose the mixing of wizard and vampire lineages. Or perhaps he is the key to a prophecy that involves both the wizarding and vampire worlds. It could also be that he has to hide his newfound heritage from his friends at Hogwarts for fear of being ostracized. There could be a lot of internal conflict as Harry tries to understand his place in this new family tree and what it means for his identity.
Another plotline might be that Voldemort somehow finds out about Harry's connection to Susanoo and tries to use it to his advantage. Maybe he wants to steal Harry's powers or turn them against him. This would create a whole new level of conflict in the story. Harry would have to not only fight Voldemort's dark magic but also protect his new - found heritage.
Yes, there are some out there. You can try searching on popular fanfiction websites like Archive of Our Own. Some might explore the idea of how Harry's lineage being related to Carlisle could change the entire Harry Potter universe, perhaps giving him new powers or a different role in the wizarding world.
One possible plotline could be that Harry, perhaps lost in the forest near Forks, stumbles upon Carlisle. Carlisle, being the kind-hearted vampire he is, offers to help Harry. They start to exchange stories about their different worlds, with Harry sharing about the wizarding world and Carlisle about the vampire society. This could lead to an unlikely friendship where they work together to protect both the wizarding and vampire communities from common threats.
Perhaps in the fanfiction, Bella has a life - threatening situation and Carlisle, in his attempts to save her, becomes overly involved and his feelings cross a line. Esme, being the perceptive one, notices the change in Carlisle's behavior towards Bella. This could then set off a chain of events where the Cullen family has to choose sides or work to reconcile Carlisle and Esme.
One interesting plotline could be Carlisle revealing his true identity to Harry and how Harry copes with this newfound family connection. He might struggle at first, but then start to embrace it as he realizes the depth of Carlisle's love and the potential for a real family.
One plotline could be that Harry discovers the existence of vampires through Carlisle. Since Carlisle has a different view on life compared to most vampires, he could teach Harry about the vampire world and how not all of them are evil. This could lead to Harry having a new perspective on creatures that are often seen as dark in the wizarding world.
One possible plotline could be how Harry and Carlisle meet in a world where the two fictional universes collide. Maybe they meet during a magical event that draws vampires and wizards together.
One possible plotline could be Harry struggling to keep up with his magical training due to his anemia. He might have to find alternative ways to gain strength for spells.
One possible plotline could be Harry struggling to accept hugs or physical contact from his friends, causing misunderstandings among them.
One possible plotline could be that Harry somehow gets transported to the world where Izaya exists and they form an unlikely alliance. Maybe they team up to solve a mystery that is plaguing both their worlds.