[She's silent, for a long moment, after that explanation. She likes that idea -- fixed points in time that cannot be changed. It lines up pretty well with what she believes so fiercely.

But soon, Rei draws in a breath.]

I wish Setsuna were here.

[A pause, before she continues, belatedly realizing the Doctor would have no idea what she's talking about.]

-- she controls space and time. Or she guards it -- it can't really be controlled, I guess. I wouldn't know. But she stays by the door of time and guards it, by herself, because it can't be messed around with. I've only been through it once, because someone was trying to change our future, and they needed to be stopped.

[Rei pauses again before she sucks in a breath, exhaling shakily.]

It must be why no one remembers this place. I've been here -- for so long, that if I had the chance, I would change so much -- so many decisions that shouldn't have been made and people that can be saved, but you can't do that, can you?

Everything happens for a reason.

[But it sounds almost mechanic, when she says it. Like she has to believe that that's why things come to pass. Nothing else will give her rest.]