She and Makoto are the closest to being "awake," in the sense that they're putting together that things about this world are off.
Possibly Nodoka, depending on how much she remembers from her manic states.
But seriously, could you imagine Yumi walking onto the rooftop, shouting "yo, what the fuck is goin' on?" and Ayane immediately screams "You didn't tell me you were fucking Yumi!" and Maya says "you're disgusting" and Yumi threatens to throw all three of them off the roof unless they take that shit back RIGHT THE FUCK NOW.