This show is impressive. I need to rewatch the episodes cause surely I haven't caught everything. Anyways I almost agree with the feeling about Shun, he will do something against someone between the society or the group, now it's hard to guess.
The night river scene was beautiful, very well done Shun, but when he touched Saki's hand I thought he went to far for "anime standards" to not raise some ominous flags. He was too straightforward.
So far I think that he knows more than he shows, more enough to know how far they could go beyond the limit to not actually cross that invisible line. But after the PV, it's more like he think to know where that line lie, but probably he misjudged it
Anyways, at a certain point he will have to stop his friends pushing forward, and stop seconding Saki, but doing so will mean going against them. Probably Saki and Satoru, having Maria as unwanted ally, who for her jealousy (?) will do something bad.
So basically I hope that he will look like he betray them, but for their own sake. I would prefer that than him following the tale demon path.