Why was Saya so mean to the girls? What was her ultimate aim?
The best I can imagine is that by teasing the students, she was able to raise their psychological trauma so that she could be stronger in the Otherworld (she's the one with the mass of cloaked soldiers at her beckoning) and better manage that universe so she could protect Yuu. I think the only thing she cares about is protecting Yuu at all costs, even if she has to be a jerk to do it.
Why was Saya so mean to the girls? What was her ultimate aim?
The best I can imagine is that by teasing the students, she was able to raise their psychological trauma so that she could be stronger in the Otherworld (she's the one with the mass of cloaked soldiers at her beckoning) and better manage that universe so she could protect Yuu. I think the only thing she cares about is protecting Yuu at all costs, even if she has to be a jerk to do it.