I don't think this is a setup, this is how she always act towards her mother. she just accepts her madness motionlessly. but who knows what's gonna happen from now on. the flashback is the final nail to the coffin, since those are scenes, if i remember correctly, in which those characters tell him he should act like a man is expected to act in a society (good parent, good professional, etc). he doesnt so its like everything is coming to punish him.
the big question here is that what's the author gonna do? she's gonna resolve koto's problem or is gonna make everything crush them both. koto's still completely bound to her mother, this is just gonna make that worse.