After re-reading some chapters I think that MC in his previous world was someone in a bad spot (duh, pretty obvious), someone that had lived with people that had to make him understand the best way to act at all times to avoid becoming a target, but he is even prety young.
Or maybe he was a profiler or studying to become one, a couple recent korean comics invested in the career so it made me remember some details about the job, like that having to do with criminals in a way that makes you think of their next move can warp your own mind, the usual stare at the abyss thing, the recent kidnapping arc made that that theory more believable.