okay theory: let's say chan is the traitor, since there are many hints pointing towards him. but what if chan is actually saving all these "missing" people? maybe as soon as he knows that someone has recollected their memories, he immediately takes them into hiding, but pretends that they are gone for good so that the authorities don't meddle in it, because they will only harm these people. also that psychiamancy thing is pointing towards seungmin, but chan has done all the 6 courses of the academy, so maybe he has the same power too?
(please tell me if you think of someone else i'm still unsure)
Hi!! I like your theory ^^ I belive too that Chan knows more than Minho...but I don't know, there are some things that bothers me like if Chan is the spy he has to be a really good actor (and a psycho) I mean for the scene of his breakdown when Sana disappear and then his overprotective/paranoia with them (He has to be really cruel to make them a family just to betray them) so I pray he is not :]
So what about the possibility of the spy being manipulate by some authority of the academy? Maybe they use students especially Irenics or anyone that know psychomancia to spy and this puts Felix, Hyunjin, Chan and Seungmin like suspects. Even Jeongin, remember the words of Chanbing about don't bad mouth about bay8 near him is still bugging me.
Maybe I'm just super paranoid because I still had this feeling of not knowing them hehe there are so many secrets....