Park Hae-jin as Kim Sul-woo, Undercover Bodyguard
Kim Min-jung as Cha Do-ha, Fangirl turned Manager
Overall, she's adorable with Woon-kwang, and the two of them have such a comfortable and sweet relationship with one another. It's an interesting dynamic because they clearly aren't platonic friends, but they also aren't romantic interests. Since Do-ha is such a fervent and unquestionable fan of Woon-kwang first and foremost, she sees him as an idol and loves him more as a fan than a potential love interest. Likewise, Woon-kwang clearly shows affection towards Do-ha, but appears like an oppa to her rather than his usual, playboy self.
I loved the scene in episode two where Woon-kwang worries about Do-ha's sprained ankle and then piggybacks her home. It's usually a romantic gesture in most dramas, but for me, I didn't get that connotation. Their relationship really is a sweet portrayal between a fan and a star (that has blossomed to something deeper), and I'm glad to see the show capture a different type of male-female relationship.
Park Sung-woong as Yeo Woon-kwang, Hallyu Megastar
No doubt Woon-kwang is bossy, petty, and prickly. However, he's also really simple, which means he's easy to read and control. In the beginning, I thought he was unimaginably rude, but then I noticed that he's only super mean to his road manager. During Sul-woo's investigation about Woon-kwang, he concludes that the star is strong against the weak, and weak against the strong. However, his conclusions seem to shake a little when he sees Woon-kwang piggyback Do-ha. Similarly, I realized that I was listening to the road manager's opinion, and after watching Woon-kwang interact with different people, I don't actually think his good-nature is for show. I think he does care about the lower staff members (maybe due to his own career history) and isn't acting that way to improve his image.
That doesn't mean he's not a jerk to his road manager, though his road manager also gets his petty revenge here and there. It makes me wonder why their relationship is like that, but maybe Woon-kwang just likes being bossy to him and they're just your stereotypical relationship. Also, he's still a typical playboy (though I'm sure there's a backstory connected with Chae Jung-an's character that will explain his behavior, some). Overall, I would argue that Woon-kwang is a good person who's really simple, and I adore him already.
Plus, Park Sung-woong looks amazing.