Why don't they just find the dirt that the manager has on that guy? They could then blackmail him into leaving them both the fuck alone and no more murder happens and they live out their perfect, kind of gothy, frilly lifestyle.
Of course if the man won't listen to reason and gets in the way of the yuri....
But why he looks so scared and distressed? Maybe the manager was protecting him from someone/something even worse? Or he had stockholm syndrome towards the dude?