In the 'Hitagi Crab' story of Monogatari series, Senjougahara says the following:
So you say, Araragi-kun. But I'm afraid I only half trust him. I have been tricked too many times. Five people had said the same thing. They'd all been liars. And... That did not seem like the end of it. Even the hospital -- I only go out of inertia. Honestly, I've pretty much given up. This world may be bizarre, but it has neither Mugen Mamiya or Kudan Kumiko. The best it can manage is Touge Miroku.
Unfortunately, I could not find either description of these characters nor at least where they are from (with exception of Mugen Mamiya) while googling. So, who are they, and why exactly does Senjougahara means by saying that this world does not have them?