Just to so you guys know, regarding that first question in the beginning of the thread, it's invalid.
You see, Tae was targeted by Gantz. And just like every other being ever targeted by Gantz, she could then see the gantzers. None of those aliens ever had a problem seeing the gantzers. It's just uninvolved people that couldn't see them. Humans. Am I trying to say Tae is an alien? No, shit no. I'm saying ANYONE targeted by Gantz can see the gantzers.
Why were those vampire dudes able to see the gantzers?
Remember those contacts they put on when we first encounter them?
Yep. That's it.
Is my answer late? Yes.
Is it long overdue? Damn Straight.