My guess is he has borderline personality disorder
It's a plot. I haw no idea of the purpose, but he has his own twisted motivations.
see now i remember when Koogi did a Q&A for KS that they were asked if Sangwoo had borderline personality disorder, i dont remember the response but i think at this point that's the likeliest possibility. i just feel so unsettled by the change. like "nice" sangwoo is more uncomfortable then "crazy" sangwoo. but both sides are pretty terrifying :3
There is truly only one question that must be asked in response to the first chapter of the new season.
WHY IS SANGWOO BEING NICE !!??
much concern...