Since I'm not familiar with this exact fanfiction, I can only speculate. 'issei is a shinso vampire fanfiction' could potentially tell a story full of mystery and the supernatural. Shinso vampires might have their own set of rules and hierarchies in the fictional world. Issei, being one of them, could be involved in power struggles, or perhaps he's on a quest to discover his true origins as a shinso vampire. It could also be a love story where his vampiric nature complicates his relationship with someone.
The unique elements also lie in the character development. Since Issei and Shinso are not originally vampires in the source material, their transformation into vampires or their journey within the vampire world allows for a lot of growth. They may struggle with their new identities, dealing with the thirst for blood, and the moral implications of being a vampire. This internal conflict and the way they overcome it or succumb to it is what makes these fanfictions interesting. Additionally, the fanfictions often introduce new vampire lore, like unique ways of turning others into vampires or different hierarchies within the vampire community.
You could start by looking on popular fanfiction websites such as Archive of Our Own (AO3) or Fanfiction.net. These platforms have a large collection of fanfictions, and there's a good chance you might find it there.
A great issei shinso vampire fanfiction to check out is 'The Dark Vampire Legacy of Issei Shinso'. This story delves deep into the history of their vampire heritage. It starts with Issei having strange dreams about his past life as a vampire. As the story progresses, he teams up with Shinso to uncover the secrets of their kind. The author does an excellent job of creating a spooky and engaging atmosphere, with detailed descriptions of the vampire world, its rules, and the characters' relationships.
Love is also a frequent theme. Tsukune may find love within the vampire community or have to deal with his previous human relationships while being a vampire. Sometimes it's a love triangle between a human, Tsukune as a vampire, and another vampire. This adds a lot of drama and emotional depth to the fanfictions. There are also themes of acceptance, both Tsukune accepting his new vampire self and the other characters accepting him for who he has become.
Well, the plot could start with Naruto being turned into a Shinso Vampire in some mysterious way. Maybe during a mission in a strange land, he gets bitten by a powerful Shinso Vampire. Then, he has to deal with his new powers and cravings while still trying to protect the Hidden Leaf. His friends might initially be scared of him, but as they learn more about his situation, they try to help him control his vampire side.
There's also 'Issei: The Vampire King'. In this fanfiction, Issei is turned into a vampire and has to rise to the throne. It's interesting because it explores his leadership skills in a new context. The author does a great job of weaving in elements from the original source material while adding a unique vampire twist.
In most shinso vampire Highschool DxD fanfiction, aside from the shinso vampire itself, characters like Akeno Himejima could be main characters. She has her own powers and personality that would interact interestingly with a shinso vampire. Also, Koneko Toujou could be important. Her relationship with the shinso vampire might involve her cat - like nature and her role in the devil society. And of course, there could be original characters created specifically for the fanfiction that become main characters as well.
In 'naruto shinso vampire dxd fanfiction', the theme of adaptation is quite prominent. Characters are thrust into a completely new environment with different rules and species. They need to adapt to survive. Another theme is the struggle for power and control. With the addition of Shinso powers and vampirism, there are often power struggles within the story, whether it's between different factions in the DxD world or between Naruto characters and the new elements they've acquired.
Well, for a fanfiction like this, Naruto could bring his ninja training and knowledge of different jutsus. Shinso's presence would add a psychological aspect as he can mess with people's minds. They could get involved in the power struggles in the Vampire Highschool DxD world. Maybe they side with a particular group, like the Gremory family, and help them in their battles against other factions. It would be a story full of action, mystery, and new friendships as Naruto and Shinso navigate this strange new world.