So wait Jake's not a gangster? What is he then? How did shin find out? I'm kinda lazy to get caught up again.
Shin doesn't hate cops. And Jake is actually a CIA agent. The main reason Shin is mad is because Jake kept the truth from him that he's not a gangster. Imagine that you are in Shin shoes, you risked your safety to be with your hot gangster bf but then it turns out he's been lying to you this whole time. If he's been deceiving you once, who says that he can't do it again? And that's pretty much summed up why Shin felt betrayed.
Top tag should definitely include kidnapping