I don't think it's going to start off particularly dark, but what modern Horror does, right? 

I think it really depends on where the players want to take it, what kind of characters they make, etc...

As the GM, it's my goal to make sure there's something for everybody. If some people want dark and some people don't, I'm pretty confident that I can provide both. 

Also. I read Gantz but never watched it. I liked the general concept of it, but it was a little too graphic for my tastes. I feel like the point of gore is to remind us as humans that we're really just watery sacks of meat, and thereby bring about an existential vulnerability that can be manipulated for more jarring horror. To each their own though. It serves pretty well as a Death Game version of Survivor.