Wonho is a confusing character. I don't understand why he chose to sleep with sponsors that he didn't really like, if he liked Min-Ki so much. It was probably a mix of the entertinment business culture, his ambitions, and taking Min-ki for granted that led to his decisions. Perhaps something was also missing in his relationship with Min-ki that made him feel unsatisfied, something which he wasn't aware of.
In the end, it seemed they were not meant to be together. If there is ever a sequel to this series, I'd like to see how Wonho and Eunwoo's relationshi plays out.