I had just read the webtoon and I really liked it, so I went for the series. First I'm gonna do some comparison then I'm gonna talk about the story itself.
I loved what they did with this adaptation because the female intern doesn't exist in the webtoon, neither does the women in power of the company. The only girl in the webtoon is Jiyeon, his friend from college, so I liked that they added more important female characters. I really missed something from the manhwa which was the fact Jiyeon had her own drama going on. When Seung Hyun was sad because of the pen, he and Jiyeon cried together because she was also suffering because of a girl. She even found herself a girlfriend later and this girlfriend was very present, so I missed her plot. I'm not sure I liked Ji Yong's acting. I get that the character was supposed to give puppy vibes and he totally got that puppy eyes, but that man smiles way too much. It's kinda creepy tbh. Overall, I really liked how it turned out and the things they added, like the art, visual effects, a reference to the webtoon itself etc.
About the story: I really liked how the drama was about their success in the company and not that cliché "boss/employee can't be together" thing. I love how quickly things went, but still in a natural way. I think their relationship was so good and I admired how Mr. Kim was already trying to change because he knew he had been a terrible partner before, so he was willing to communicate. Even when he didn't understand his partner's side, he talked. He said "I don't understand, but I want to" and I think this is beautiful. I also liked that he got him a permanent job fairly. It was cute and warm.