Forgot to sign in, just to add that Wonho's behaviour to Min-Ki is condemnable, but I guess we are able to try and get more of an understanding why he is behaving like this, and what his situation is. Regardless of Wonho's frustrations, it must be mortifying knowing that his partner isn't being faithful to in, and this is down to the pressures of the industry that he too is in. Min-Ki staying with him and why, has been discussed by others, it's understandable that he can't just leave him, but it's probably for the best if they move on from each other, but that is likely just an idealist outsider opinion, who knows if the author will keep them together. It does seem rather cliche to have the naive bright young thing be the one to show Min-Ki the grass is greener, so hopefully there will be more fleshing out of Min-Ki and Wonho's relationship before they split, if they ever do.
I think people are forgetting just what exactly is going on here. Wonho isn't a teenage girl rookie actor or idol, but he too is a victim of the prostitution that is rampant in the South Korean entertainment industry, which has resulted in actors and idols taking their own lives, as they can no longer cope with being raped, sexually exploited usually on the orders of their management. Work place bullying, nepotism and sex work is hardly unheard of in SK, but "sponsorships" are one of those open secrets where basically the wealthy influential men and women are untouchable, and if the actor or idol wants to secure work or pay of the massive debt that is occurred from them trying to debut or maintain their career from their management, then they have limited choice. A wealthy or influential person can provide, but on the grounds that there is a return, which is usually sex. Wonho says he has had more sponsors than Taeyoung's cousin, this would suggest that he has spent the majority of his career being prostituted, even if he does retain a degree of agency, in order to work. The stresses of this, have resulted in him becoming controlling of Min-Ki, as Min-Ki is the only rock he has. He's presumably studied to be an actor, and trying to make a career of this whilst dealing with sponsorships, yet someone like Taeyoung, who is a model, not an actor (and is also an influential sponsor's cousin) gets offered a big role in a film without much of an acting record.