why sex comes first before all the important talk? all of these characters in manhwas alwa...

Um? Most abusive relationships in real life occur like that. Why would it.be any different in fiction?

Seems like it was more to do with asserting his "claim" on Min-ki, as he's been apart from him, and knows he's sharing a room with Taeyoung. He's done other in the context, abusive things like turning up at his work to keep an eye on him, rather than be a support, and have sexual contact which given the setting could cause a major scandal if a pap saw them.