I think you're misunderstanding something there jin never "went crazy" he was insane from the start the nice guy in the beginning is just his cover up
I kinda doubt it, he does seem genuine in some parts even though most of it is an act. We don't know for sure yet anyways, and as far as current jin knows, he really does seem like the only person who loved Noah for who he is. MC is literally a spy sent by him to retrieve documents, there's no way he would see their relationship as genuine.
I think he really did hope to find escape in Noah from his responsibilities as an upcoming district leader which is why he faked the arm injury for so long, but once he returned to society he realized that he would have to keep shackles on Noah to continue the peace he had with him, hence the introduction of Peter and all the instability that follows after
I fucking hate the comments complaining about the plot... If you want to read braindead mindless smut, there's plenty to choose from on this website. Stop acting like a fucking retard the one second a yaoi requires you to use braincells.
Also, Jin is interesting as hell. Honestly I love this universe as it is, but I really want some kind of AU side story where Noah never ran away and Peter was never introduced. I wonder if Jin would still go crazy?