If someone is to die against Oni boss, right now, it might either Kaze or most likely Old Man. Everybody else can go back, though Kaze should be alive to give his points to free the little kid.

Whenever they are to face the Vampires, I look at this like a big event with a match already booked between the bossy handsome blonde and Izumi. Kei will obviously have to face against Akira. If Old Man survives, I have a hunch about him facing the oldest looking vampire ( yeah, this sounds kind of stupid ), Sakata and a ressurected Sakurai teaming up against the hairy ( hmm...maybe GANTZ will nickname the vampires like this, sort of like Grumpy and Rowdy Aliens ) vampire, and Kaze against the big one that looks like an american. I'm not sure about Reika's chances on these fights, I can now only imagine she'll play a role in Kei's fight with Akira.

After the vampires, I think this could all come to some apocaliptyc close.