A powerful vampire lord could be the main antagonist. This vampire lord could be ruling over a hidden vampire society and sees Lupin as a threat to his power, especially if Lupin is starting to gain vampire - like abilities.
Another theme is the idea of redemption or change. Some fanfics explore the possibility of Lupin turning over a new leaf, or Zenigata realizing that there's more to Lupin than just being a criminal. This can lead to some really interesting character development.
One idea could be that Lupin discovers he has a vampire ancestor and starts to develop some vampire - like abilities which he has to learn to control while on a heist. Another could be Lupin teaming up with a vampire hunter to steal a powerful vampire - related artifact from a group of evil vampires.
One popular lupin the 3rd x zenigata fanfic is 'The Unending Chase'. It delves deep into the complex relationship between Lupin and Zenigata. In this fic, their cat - and - mouse dynamic takes on new dimensions as they are forced to work together in an unexpected situation. It's full of action and some really interesting character interactions.
The 'cagliostro gran granblue fanfic' is likely a piece of fan - made fiction set in the Granblue Fantasy realm. Since Granblue Fantasy has a vast and rich universe with many characters and concepts, this fanfic might be an attempt by a fan to expand on the existing lore. Cagliostro could be the main focus, perhaps with the story revolving around their powers, their origin, or their role in a particular plotline that the fan has devised. It could also be a crossover within the Granblue Fantasy universe where Cagliostro is paired with unexpected characters to create an interesting and new narrative.
You can try looking for it on fanfic platforms like Archive of Our Own (AO3). There are a lot of Granblue Fantasy fanfics there, and you might be able to find the 'cagliostro gran granblue fanfic' among them.
Yes, Lupin is based on a real story. Lupin is inspired by the fictional character Arsene Lupin, created by Maurice Leblanc. The character has been adapted into various forms of media, often with elements that draw from real - life inspiration such as the settings, the social context of the time, and some of the heist - like situations that could be related to real - world criminal activities, although highly fictionalized for entertainment purposes.
Arsene Lupin is a fictional character, not a real person. He was created by Maurice Leblanc. Lupin is a master thief and a very clever character in detective fiction. His adventures involve outwitting the police, stealing valuable items in elaborate ways, and having various escapades across France and sometimes other parts of the world.