What can I say, the MC is a sociopath, a guy that enjoys murder, betrayal and so on, yeah, I would want to kill all the freaking people that were involved in summoning me to a fantasy world, but that's as far as I can sympathize. The author tries to justify this mentality with the game kind of mindset, that that reality ain't real to the MC but he ain't apathetic about the people in that world, they ain't irrelevant, instead he enjoys plotting murdering, lying and so forth just for the sake of it or a marginal benefit. I don´t find the MC's actions justified enough to put up with them, he's just a piece of sht..
As for the story... can't say I like it either, a "save the world from the demon" setting that became a personality correctional sim? An instructor that does nothing to the story or to the actual MC (when he goes on a killing spree), but wag her finger and so on... (I know what I say makes little sense but it does in the context of the story). The premise itself is pretty dumb too to be honest, another piece of sht (a presence) that kidnapped a guy from his normal life, a normal life, one where he wasn't apparently wicked (meaning he's too is a normal "centered" man) and when after his efforts to survive and go back he got twisted by the crap world he was thrown into (against his will, meaning that, lets say, he became ruthless and morally gray in order to cope with his new reality), that presence, god?, admonishes him for being a bad guy?... cut the crap, whatever he became it's thanks to that presence, you don't send an innocent to prison and when he comes out become surprised that he's more violent, it's expected, and it's the fault of the one who sent him to prison wrongly.
@Nickthequick actually I'm saying the same thing as you (I tried to edit the review and make myself a little clearer), I think that it makes no sense for him to get into that save the world morality and that the MCs loss of morality is not entirely his fault and is to some point justified. I just don't like an MC that enjoys murder, deception, treachery and so on, one thing is doing unmoral things to survive and another is to enjoy it.