So far it's mainly a Ranma/Vampire Princess Miyu crossover so far, but Hellsing and Sailor Moon will be added to the mix. Ranma and Kasumi are not normal vampires but vampire shinma (and not affected by the sun, garlic, crosses,...)
Ranma is Miyu's sister as well as son/daughter. Sounds strange, but it's explained in the fic and even makes sense B)
The biggest turnoff for most people here will probably be that Ranma prefers his female body (and has so for a long time, just keeping up appearances to fool his father and the other morons) and Kasumi admits that she's bisexual but has a preference for women.
It's a rather well written and the story flows easily even if it's a bit rushed. The thing that annoys me though is 'Nodoko' and 'Kodashi'