There doesn't seem to be a rule as to how many need to be in the area. One appears to please it.

[At least there is that small favor. Mukuro is not exactly a social butterfly. He much prefers his solitude or a small group of trusted companions. But there hadn't been anyone here that fell into that category.]

It's not a matter of want. It is a need. I certainly don't want to be down in that hideous casino any more then I need to be.