One manga that could be similar is 'High School DxD'. It features supernatural elements and a focus on a group of students with special powers and their adventures.
The ending of Rosario Vampire manga is quite complex. The main characters face some major challenges and their fates are tied up in a way that leaves readers with a sense of closure but also some room for interpretation.
The Rosario Vampire manga ends with a climactic showdown and resolutions for the main characters. It leaves some room for interpretation but offers a satisfying conclusion to the series.
The Rosario Vampire manga is pretty clean in that aspect. You won't find any nudity. It's all about the supernatural adventures and relationships of the characters.
I don't have the exact figure for how many Rosario Vampire manga books exist. It could be around 10 or more. The series was popular and had multiple installments over time.
One possible fanfiction could involve a crossover between Rosario Vampire and Arrancar. The unique powers and characteristics of both vampires and arrancar could create interesting plotlines. For example, a Rosario Vampire character might encounter an arrancar and initially mistake them for a normal vampire. This could lead to a series of misunderstandings and battles as they figure out each other's true nature.