@red_bean_casserole Hayase wanted to have Fushi's child, so when she failed she started the Guardian Corps with the express purpose of keeping Fushi alive so one of her heirs could could eventually complete her goal.
As for why the one knocker who was constantly passed down Hayase's family...
I'm getting the distinct impression that the rampage Chiyo saw was because one of Sakura's lieutenants goes over her head and does something to Rokudou and not because Rokudou's mark "stopped working."
Not that she isn't being incredibly entitled and stupid, but Viola's thought process makes more sense now at least. Not only was she spoiled her whole life, but the only Demon Lord she knew before this was her father who was able to last longer than normal through sheer effort and support. So...
It kind of feels weird that it took 32 chapters for someone to actually explain to Myne what the consuming even is. Especially considering it's apparently something so important that the Temple will go out of their way to try and get their hands on people who have it. With how careful Benno is...