A coven of ancient Vampiresses need a male virgin to drink his blood
to gain more power and youth. Ranma is selected. Using their superior
vampire-speed and vampire-strength, they capture Ranma and bring him
to their stronghold. But Ranma's spirit is too strong, but his flesh
is weak, so Ranma's soul appears before Emma-o (Kami of Underworld and
Judgement), which Ranma sees as the DBZ version. Emma-o gives Ranma
the choice (a) go to Heaven, but give his power to the Vampiresses OR
(b) return to Earth as an Vampire and an Agent of Emma-o.
As an Agent of Emma-o, Ranma would need to deal with the
overpopulation of spirits that endanger the World of the Living, such
as Vampires, Demons, Spirits, and the like...

As an Agent of Emma-o, Ranma would be mostly soulless, with Emma-o protecting
Ranma's soul inthe Underworld, and Ranma would be a Daywalker and immune to
weapons of Faith. But, he would have the blood-hungry, although, in time, he
will be able to absorb ki instead.

Ranma will hunt the undead and the damned...
Others, not understanding or uncaring, will hunt Ranma as well... such as
Ryouga and Tatewaki
Many will seek Ranma, either for his suppose immortality or fear him...
One day a year, Ranma will be forced back into Emma-o's presence... where he
will train with Martial Arts Master that have pasted away...
Ranma will also have the ability to see the dead-spirits, such as Mrs Tendo,
who is trapped on this World by her Family that won't let her go... Mrs Tendo
can communicate with Ranma, and he her... Mrs Tendo isn't happy with her
Family.... Soun, for not letting her go, Kasumi for being so callious and
trying to replace her, and Akane for her pervision and uncontroled temper...
Of course, none of the Tendos, save Nabiki wishes to hear that...