I'm definitely confused by all the 5-star reviews because this drama was mediocre at best. The only reason I finished it was because I had nothing else to watch and I like Son Ho-Jun. Almost everything about the plot is super predictable, and there were definitely lots of cliches. I agree with some other reviewers about the female lead being annoying at times and things just not really making sense. After you find out who the father is, there's really no reason to finish the show haha.
*spoilers*
I agree with everyone else who seems frustrated about the fact that if the main leads had had a simple conversation about their misunderstanding in their youth, literally none of the drama would've happened lol. And the part where Dae-O leaves for two years... such a typical k-drama cliche, but I feel like in this context, it really didn't make sense.